well online chess is a great way to put a ton of work into chess without ever forcing yourself to do blindfold tactics which is necessary in any tournament in just about anywhere in the world.
Should I continue playing online chess?

It's a great compliment to tactics trainer for that reason. Also, analysis board usage is optional. If you enjoy it, keep playing.

The fact that there is the analysis board and the option for a cheating opponent to beat a non-cheating one by using a computer ruins the idea for me. If I want to lose to a computer, I'll just run some local software on my computer.
If I can't play other people who are legitimately at the skill level of an accurate ELO rating when I play online chess, then what's the point? I'm sure one could say you learn anyway, but still. OTB or blitz for me, and even blitz is risky. Probably pretty hard and relatively rare to cheat at bullet, however, that's too fast for my tastes.
Playing online chess is the only way to enjoy a long game, but I noticed that most people don't take it seriously and simply blitz moves.
Why care? At the end of the day, they play moves according to their rating.

after you get out of provisional (assuming you beat the players who make blitz moves) you'll get paired with players more in your range. If they still don't take it seriously just keep winning until you move up to someone who does.
Playing online chess is the only way to enjoy a long game, but I noticed that most people don't take it seriously and simply blitz moves.
Why care? At the end of the day, they play moves according to their rating.
Yes but if I don't play with someone who play seriously why play? I don't learn anything

You learn from every game if you want to. If they "dont play seriously" then focus on winning quicker, and learn to take advantage faster. My theory about cheating with computers and all that: If they want to use computers, they won't improve, at best memorize some opening moves and repeat it, but one specific opening doesn't decide how good you are, and certainly not one game. So aside the fact they're still the crappy player they really are, you'll get better because you learn from your mistakes. A lot of users on chess.com are busted daily, so unfortunately it's common practice. As for ratings, the change in your rating is immaterial, if you're as strong as your rating says, you will get back to it soon enough.
Playing online chess is the only way to enjoy a long game, but I noticed that most people don't take it seriously and simply blitz moves.
Why care? At the end of the day, they play moves according to their rating.
Yes but if I don't play with someone who play seriously why play? I don't learn anything
If they play strong, it really doesn't matter if the take it seriously.

after you get out of provisional (assuming you beat the players who make blitz moves) you'll get paired with players more in your range. If they still don't take it seriously just keep winning until you move up to someone who does.
Within a few games your score will match up with players similar to yours. At least at chessbase (I"m unfamiliar with here, sorry!!) they do keep a close eye (maybe not real close??) on cheating and those players are downgraded. Your score will be a composite of all the players you play and I feel an accurate reflection of your playing strength.
Should you continue to play online. If you enjoy it.!!!!!
Playing online chess is the only way to enjoy a long game, but I noticed that most people don't take it seriously and simply blitz moves.