Why is it often said Bitcoin doesn’t have the capability for smart contracts when stuff like Stacks exists?

Am I missing something? I hear it reiterated throughout crypto spaces, but it seems Stacks, Lightning Network, etc. and others effectively provide a way to build on top of Bitcoin. Is there some huge limitation to this? Or is it just not really talked about much within the Bitcoin community and therefore not well-known?

Edit: just want to add I didn’t know Stacks had their own token and the reason I’m asking is because in a lot of spaces this seems to be the most common FUD I encounter. Thanks for all the responses!

Edit 2: Not sure why I'm getting downvoted when I'm just trying to ask some questions. A large part of my overall financial portfolio is in Bitcoin. I'm just trying to understand where smart contracts are at in the BTC ecosystem presently from people who I presume have more experience with them.