I really like the idea of gleam but I don't want to hand implement serialization for every type (even with an LSP action) in 2026.
Dart has the same glaring issue (yes, yes, you can use a codegen library but it's not the same).
I rarely serialise every type in my gleam code, My quick back of the napkin math is less than 5%.
Biggest issue with this language. But... fairly trivial to implement codegen with gleam/glance[0]. No good libraries do this well right now (e.g. support for discriminated unions).
[0] https://hexdocs.pm/glance/glance.html