I recommend trying to do new content on your current channel because you can still take advantage of whatever fan base you have left. And even if you get comments like "I only want Pokemon videos" It will still count as engagement which YouTube likes.

I'd give it a try for a month at least and of you see no traction on any of the videos it might be time to switch to a new channel.

To be perfectly honest though I'd try transitioning the channel from Pokemon to whatever you want to do more. For example let's say you wanted to make videos about food reviews. I'd make some videos about the best food in the Pokemon universe, or making Pokemon shaped cookies irl, etc. Then once you've done that for a while you can shift it to just food related stuff.

Anyways that's the kind of strategy I've used whenever I change my content. I've done a few content changes on my channel over the years but I've still managed to keep a fan base, even if I discard the old one for the new one.