With the rules and technology today, it would take a very large team of players with an even larger bankroll to be successful enough to justify the time and effort. People have to eat and hotels cost money (only a few would ever get comped). There may be a few individuals or small groups making a living at it these days, but they are not making a good living at it.
I taught myself and practiced for years to count cards at Blackjack. I got pretty good. My wife and I had some fun with it. But that is just it, it's for fun. I kept track of winnings and losings in monthly trips to Reno. We only played < or = to $25 tables. I'd count and she'd jump bets or dive for us. We lost big on occasion and won big on occasion. But for the tiny edge you can eek out when the deck gets just right on some occasions, you have to be playing a lot of money and be playing a lot of hands to take advantage of a 1.5% to 3% advantage over the house.
If you are wealthy enough to start a career in card counting, you are wealthy enough to not need a career at all. All others are posers and pretenders.
Successful card counting rings are a myth these days. The casinos still don't like it but nobody gets “back roomed” for it.
Some people are very good.