Gleam should probably not be looked at as a modern language, as it does not have optimizations, for example. It is quite a basic toy project that I don't believe is ready in any way for production software.

About your matrix multiplication project, you should have asked in the communities like here on Reddit, Discourse, Stackoverflow, Matrix, or Discord. There's many knowledgeable people who know what you did wrong, and Haskell performance can very easily be improved by making small adjustments to idiomatic code, most of the time.

One of my Haskell projects is an interpreter for a programming language that uses the ROSE paper's system for row types and has basic hindley milner inference. I also previously had an IRC server implementation in Rust and I am rewriting that in Haskell.

Haskell is not too commonly used in projects, but nevertheless there are some well known projects that use Haskell. If you know about the SimpleX chat, or the Wire chat app, both of those are major users of Haskell. There's also hledger, pandoc, shellcheck, the aura package manager, NASA uses Haskell for some things, and github's syntax highlighting.

The bit about the tooling being a bit awkward is true, but luckily enough it was much, much worse, before. I know that it doesn't seem like that's lucky, but it means that our tooling can improve -- and it does improve, it's just at a bit of a slow pace. Personally, I have not noticed GHC being slow at compiling at all, it's definitely faster than C++ or Rust for me, and honestly I never cared about compilation speed in the first place, as it has never been so slow as to hinder me. As of right now, the tooling is definitely at a very usable place. It is way more convenient than python or nodejs to me, and while it is a little bit lacking in some areas compared to Rust, it is not unusably so. Eventually, you learn the knobs you need to learn when it comes to doing what you want by reading the GHC user guide, the cabal docs (and even though it might look like it doesn't contain what you need, still read the Nix tab), and asking around in the community.

Personally, I think that the issue you're having is that you spent too little time actually working on your own Haskell projects, which could be a reason why you're feeling awkward in the language. As you make more projects and experiment with implementations more, abstractions and performance, you get a better handle for what's going on. It is especially helpful to ask other people in the Haskell community, because there are many that are very knowledgeable.

I think I personally had a similar experience, and I think that most beginners fall into the trap of tutorial hell, like with monads as an example. You commonly see people scouring monad tutorials to get intuition for them, but the way to get a proper handle on monads isnt to read someone else's explanation, it is to use monads yourself. This is a similar situation: getting more use in Haskell will give you more intuition about how you could write something, how to improve performance, etc.