LIVE Poker is still very profitable if you can find the right game. The problem is getting into good games if you don't live close to several
casinos or have connections to private games.
Online is almost dead above 100NL, so it's hard to make big money. You also have the problem with bots, RTA, and collusion.
Around $1,000 USD is still possible to grind out if you have some talent and play a lot of tables and several sites. But you have to treat it like a job, so it is easier to make more money in other ways.
Some pros are still online, but they often sit and wait for the fish or play "high-stakes" MTTs, which have enormous variance unless you are part of a stable.
I consider
online poker almost dead unless you play for fun and/or some extra pocket money.
If you have to go full GTO, it is almost certainly not good, since it means you can't find a way to exploit your opponents' mistakes to the max.
GTO is good to know, but it is mostly a way to defend yourself against other GTO players/pros. Against fish, you don't use it, of course. And without fish, no big money in poker.