I have a question. If everyone has to able to beat their current limits to move up in stakes, how are there any fish if everyone should be playing decent poker?

Not everyone moves up in stakes, some people buy in for a lot and just gamble

Because not everyone starts off at low stakes and works their way up the ladder. I'm sure there are plenty of beginners who hop into 50NL or 100NL either not knowing what they're doing or just because they have the money.

Also fish on heaters who don't practice good BRM and move up too fast. They usually crash and burn quickly tho ...

An extreme example ... (I checked this one out cos there is a big thread about this guy in NVG)

As the others have said, it isn't required that you beat a limit before moving up.

There are fish at all stakes, including nosebleeds. Highest I have played is PLO400 and £1000 BI live tournaments, and I can tell you there are fish there for sure.

Obviously though, the higher stakes you play the better the regs will be on average.

Most professionals with a decent job that plays casual poker has zero interest grinding micro stakes. And there are many of us.

Don't forget the aggressive nature of bad players at higher stakes. Someone who occasionally spew bluffs is much harder to deal with than loose/passive who only takes aggressive action with massive hands. Go watch mid stakes or higher games. Even most of the bad players fight for pots. In lower stakes games, the bad players just call off all their monies.
If this were a rule, poker wouldn't exist. Some people have money and enjoy gambling. Advantage gamblers provide a service, keeping games running for recreational players to visit. The whole "must move up through the limits" concept leads to feelings of entitlement and the idea that you've earned your place on the pyramid. Poker players aren't samurai. Once you move up into ranks where you play with pros, you'll find that their "horrible competition" tend to crush at life, doubly so when compared to mid-stakes+ poker players who are trying to make a living. If you can just afford buy-ins in a 10/20 NL game, you're likely winning at life (or spending yourself broke as a degen with a bad habit).

I used to play in decent sized home games with really nice people who were horrible at poker. Talk to them about what they do, how they invest their money, etc. Life was already crushed. Poker was an inexpensive hobby for them.

Binking tournament

Also aiming to play with fish isn't exactly everyone's first goal. Its nice to sit at a table with more regs especially live IMO

I guess if you hate money, sure.

I have friends they earn more than 6~70k a year in their profession. I don't think they go to play lower than 50NL. Even they do,when they lost few buy-in they probably just go to play higher stake.

Also there are fish or even tilting regs who move up to chase losses. My advice would be: DO NOT FOLLOW THEM UP

In 2 months there's going to be some nice soft high-stakes games in Vegas. There's no prerequisite (other than having the money) to play in a game. There's many white collars that have no problem dumping a few racks of black while in Vegas. Good advice for beginners is to focus on moving up (properly, obv) and not become a complacent 20-tabling small-stakes nit.

The best time to shot-take online or live is to follow a known bad player up a limit or two. The process of moving up shouldn't be about waking up one day and deciding that 25NL is for fools, you're a 50NL player until bust. It should be about adding the next limit higher into your game selection. Thus, a live 2-5 player sees two soft spots in the 5/T game and decides to play the bigger game. Next day, the 5/T game is reg filled and he happily takes his 2-5 seat knowing that profits are coming and his BR isn't at risk in the at best 0EV variance fest.