Is it still possible to earn a fortune in Bitcoin mining?

Mostly no, the competition is too great. You can join a mining pool and share on what's mined. But even then it's iffy, if you can't access cheap energy.

The pot of gold is waiting for the person who can figure out the killer app for it but mining is mostly a big miner's domain now.

I know of a guy who mined 50 coins overnight while playing with the mining software on his machine about 10 years ago. It's now worth over $2.5 mil and he's not done. He's holding it until he retires. His big advantage is that he does not need the money and is not counting on it as a retirement fund so he can hold it thru all the dips without feeling like the world is coming to an end.

I feel like you already know the answer.

Providing you keep as much of the bitcoin you mine as possible.

If you sell it all for cuck bucks, you're not gonna make it.