I always obsessed over dinosaurs as a crazed little kid and eventually developed a pretty strong fascination with beasts and cavemen when I reached my awkward teen and young adult years, but for some odd reason I'm not too overly fond of this movie in-particular (I know, I'm a weirdo). I'm not entirely sure why but I'm guessing it's probably got something to do with the fact that I personally enjoy dinosaur- and caveman-related stuff more when they're both done separately, as I'm very much into learning about the actual real-life events which truly took place way way back in prehistorical times (I can't help but be an avid prehistory enthusiast, through and through). But this weird unexplainable feeling of mine seems to only apply to live-action films/series specifically and not animated features/shows, so that means cartoons like Hanna-Barbera's The Flintstones (1960), Blue Sky's Ice Age (2002), DreamWorks' The Croods (2013), and Genndy Tartakovsky's Primal (2019) are all fine by me. This might be because I believe you're allowed to take creative liberties through the format of animation with artistic license (there's no limit to this expressively imaginative medium).
A perfect analogy for how I feel is to describe it like this; most people would prefer to eat a nicely cooked dinner (a warm meal) first and THEN have a scrumptiously sweet dessert (cold ice-cream/cake) afterwards - instead of just slapping them up into one unappetising combo and ingesting both all at once within the same timeframe (two very good individual things on their own that simply don't go down well together). Let's put it another way, shall we. If I wanted to watch a dated-yet-classic dinosaur film, I'd watch Jurassic Park (1993). But if I wanted to watch a dated-yet-classic caveman film, then I'd watch Quest for Fire (1981). I wouldn't want to voluntary watch something like Ringo Starr's Caveman (1981) or Raquel Welch's One Million Years B. C. (1966), with the latter feeling like just as much a comedy spoof in and of itself (although, I am partial to certain satirical parodies). The eras of the Mesozoic (dinosaur age) and Cenozoic (beast age) are equally awesome and fascinating timespans, but I just prefer them when they're apart from one another (quite frankly, it might only be just me alone who possesses this mindset).
As for judging this movie on its own merits, though? Eh, it's alright enough. There's definitely some decent entertainment value to be had out of sitting through at least a single viewing of it, but that being said I personally found most of the scenes in here to be kind of dullish and repetitive and I thought most of the characters were pretty flat and unengaging (but that's just me). In all honesty, my own opinion is that this schlocky pseudoscience-fantasy isn't really one of Harryhausen's best works (I think his '50s giant monster/alien invader B-movies are more my kind of thing). I've also been in quite a state of fluctuation over what rating to give the film, constantly floating back-&-forth between either a 6 or 5 out of 10. But then I suddenly remembered how I unironically enjoy all the silly old kaiju flicks from around the same time, which heavily incorporated all sorts of wacky hyperrealistic plots involving fantastical prehistoric aberrations within their own fictional world, and so with that I lumped this into the same bonkers creature feature category as those (finally settling on a decent 6/10, which seems fair enough). I think this movie would've greatly benefited from being more of a classic time-travel adventure featuring an archetypal professor and explorer characters as the main leads, with them going around messing up by accidentally changing the main timeline throughout natural prehistory (just saying that this would've at least offered up an amicable explanation as to why the two displaced eras suddenly merged together into one).
SIDE NOTE; just a funny piece of factual trivia for all you diehard Harryhausen film buffs out there from a self-described palaeo-nerd (that being me). Dinosaurs died out well before 1,000,000 years ago B. C. E. Ever occurred and proper humans hadn't yet fully evolved by that point, either. Instead, what was around were an ancient lineage of upright-walking apes which had direct ancestry to humanity's beginnings - so this specific temporal range would've seen the rise of when our "missing link" origins came about (just another fun example of how this film has nothing to do with its actual titular date).
A perfect analogy for how I feel is to describe it like this; most people would prefer to eat a nicely cooked dinner (a warm meal) first and THEN have a scrumptiously sweet dessert (cold ice-cream/cake) afterwards - instead of just slapping them up into one unappetising combo and ingesting both all at once within the same timeframe (two very good individual things on their own that simply don't go down well together). Let's put it another way, shall we. If I wanted to watch a dated-yet-classic dinosaur film, I'd watch Jurassic Park (1993). But if I wanted to watch a dated-yet-classic caveman film, then I'd watch Quest for Fire (1981). I wouldn't want to voluntary watch something like Ringo Starr's Caveman (1981) or Raquel Welch's One Million Years B. C. (1966), with the latter feeling like just as much a comedy spoof in and of itself (although, I am partial to certain satirical parodies). The eras of the Mesozoic (dinosaur age) and Cenozoic (beast age) are equally awesome and fascinating timespans, but I just prefer them when they're apart from one another (quite frankly, it might only be just me alone who possesses this mindset).
As for judging this movie on its own merits, though? Eh, it's alright enough. There's definitely some decent entertainment value to be had out of sitting through at least a single viewing of it, but that being said I personally found most of the scenes in here to be kind of dullish and repetitive and I thought most of the characters were pretty flat and unengaging (but that's just me). In all honesty, my own opinion is that this schlocky pseudoscience-fantasy isn't really one of Harryhausen's best works (I think his '50s giant monster/alien invader B-movies are more my kind of thing). I've also been in quite a state of fluctuation over what rating to give the film, constantly floating back-&-forth between either a 6 or 5 out of 10. But then I suddenly remembered how I unironically enjoy all the silly old kaiju flicks from around the same time, which heavily incorporated all sorts of wacky hyperrealistic plots involving fantastical prehistoric aberrations within their own fictional world, and so with that I lumped this into the same bonkers creature feature category as those (finally settling on a decent 6/10, which seems fair enough). I think this movie would've greatly benefited from being more of a classic time-travel adventure featuring an archetypal professor and explorer characters as the main leads, with them going around messing up by accidentally changing the main timeline throughout natural prehistory (just saying that this would've at least offered up an amicable explanation as to why the two displaced eras suddenly merged together into one).
SIDE NOTE; just a funny piece of factual trivia for all you diehard Harryhausen film buffs out there from a self-described palaeo-nerd (that being me). Dinosaurs died out well before 1,000,000 years ago B. C. E. Ever occurred and proper humans hadn't yet fully evolved by that point, either. Instead, what was around were an ancient lineage of upright-walking apes which had direct ancestry to humanity's beginnings - so this specific temporal range would've seen the rise of when our "missing link" origins came about (just another fun example of how this film has nothing to do with its actual titular date).