While the original Switch's Joy-Con and Pro Controller accessory are both compatible with the Switch 2, Nintendo producer Kouichi Kawamoto says in a blog post posted after the Nin

" Nintendo Switch controllers can be used wirelessly and are also compatible with Nintendo Switch 2 exclusive games, but cannot be used if the games requires features unique to Joy-Con 2, such as mouse controls." Nintendo also mentions how some other features on these older controllers won't be available on the Switch 2:

When moving from one generation of consoles to another, it’s not always guaranteed that old accessories will work with the new system. So, do old Joy-Con, Pro Controllers, and other accessories