I don’t think you can answer this question for Pokemon in general, I think it would be species specific.
Meowth is clearly of human intelligence, for example. Hell, he’s smarter than Jessie & James.
Then you have the extreme end, where Alakazam has an IQ of 5000. We’re basically ants to them.
Not to mention pretty much every psychic pokemon in the anime can have proper conversations with humans using telepathy.
But does intelligence grant them human rights? Since we still regard intelligent animals as animals.
There isn’t any animal that is even remotely comparable in intelligence to what we see Pokemon capable of, so it’s not really fair to make that comparison.
Dolphins and Chimpanzees are widely considered the next most intelligent species after us, but they’re still far below us. You can teach a Chimp basic sign language, but you still can’t have a proper conversation with them, let alone come up with complex plans with them.
By comparison, Meowth is not only capable of all that, he’s better at it than J&J; iirc, most of their plans that almost succeeded were his ideas. Plus he’s extremely capable at subterfuge, considering he once successfully convinced Ash & Co. that he was done with Team Rocket and gained their trust, only for it to be yet another scheme. Not to mention his ability to operate highly complex machinery.
And mind you, there’s zero indication that Team Rocket’s Meowth is any more intelligent than any other Meowth, he’s just vastly more ambitious. They very clearly show that his more human like tendencies are a conscious choice, not something inherent to him. Other Meowths could learn English, they just choose not to(and at least one thinks TR Meowth is weird for doing so).
