There's no way to even get a job without understanding monad transformers.
If true that's sad and hopefully effectful will bring than to an end https://github.com/haskell-effectful
I hear this opinion every so often but I just don't think it's really the case. Many libraries out there expect you to use Monad transformers. You might try to keep MTL out of your own application code, but you'll find that the rest of the ecosystem favors it. You can still use these libraries without MTL, but it's often not ergonomic and therefore not really an option.
Effect systems and monad transformers are advanced topics. They're possible to use in my language yet most people do not and can still write software.
Certainly no need for them in Haskell to be successful. You can just program at the lower levels of abstraction common in other languages.
The only difference is that Haskell's community tends to emphasize abstraction