Too many new OAuth scopes

No not really, basically following the oAuth spec here and this is a “problem” for anything that does oAuth, new feature = new scope = need to get new tokens so you can use new feature.

Twitch adds a new thing, Twitch needs to scope that new thing.

As a user might not want to have a tool access the new thing, and a developer might not want to request access to the new thing

Only declare the scopes you need for your tool to work

If your tool implements a new feature, then you need to communicate that you support that new feature and get new permissions accordingly

If users are logging into the tool to use it anyway then getting new scopes is trivial

That is incredibly dangerous and unlikely to come to pass.