…it’s 14 minutes long, do I have to watch it?
Okay, so, Mew is the “New Species” Pokémon in the sense of “newly discovered” – she’s the most recently known of the generation I Pokémon. When Treesicle says that Mew is the ancestor of all Pokémon, he’s… basically quoting direct from the games; it’s not wrong or even controversial (I happen to have my own ideas about that, but this isn’t the time or place). If you believe what the games say about Mew, and if you also believe that Pokémon “evolve” in much the same way as real life forms do, then something like what he describes must have happened. As for the line about trilobites, well, it is a bit silly and could have been researched better, but the point he’s trying to make – that evolution is basically a process of divergence and diversification – is perfectly sound, and the error has no real impact on the argument being made.
The basic point the video makes… well, I more or less agree with it; I’ve said similar things before myself. I think it’s more complicated than Treesicle puts it, because “intellect” is supposedly something that lots of Pokémon do have in equal or greater capacity than humans (most notably Alakazam). We do somehow have to explain why those highly intelligent Pokémon seem to lack humanity’s capacity for organisation, leadership and creativity – and, for that matter, why they evolved heightened intellect at all if they don’t use it to create technology and form complex societies. The essential point is fine, though; I don’t see what you find so objectionable about the video.