it now primarily has alt-right, conspiracy and terrorist uses.

Assuming you meant “users” - I highly doubt that the users you described are even a large minority of Telegram’s user base. They’re highly publicized but that’s it.

Telegram is just a tool. How is saying “don’t use it because terrorists use it” different from saying “don’t use a screwdriver because terrorists use screwdrivers.”

Telegram isn’t a secure messenger like Signal, Matrix, the others you mentioned, or other e2ee options out there. It has an extremely limited secure mode that is useful if you need to have a one-off conversation, but that’s it. But if you don’t need a secure messenger and instead want something to replace Twitter, Discord, other social media, or to serve some other purpose, then it’s fine for that.

founder is sketchy

I’m not familiar with the folks associated with the other apps you mentioned, but Signal’s former CEO and co-founder, Moxie, is a pretty dubious character, too. Signal is anti-FOSS: you can’t use their servers if you fork the client; they won’t federate if you host your own servers; they’re opposed to being on F-Droid or even providing reproducible builds; and they have a history of failing to update their repos in a timely manner, to the point that clients built from source couldn’t even connect to their servers.

That all said, I still use and recommend Signal.