There are some serious legacy issues with the LaTeX ecosystem. The lack of being able to version individual package dependencies for a document is a huge one. You’re at the mercy of lots of independent packages which often have complex webs of interdependency.
Probably the biggest mistake was the choice to abandon the idea of having a LaTeX 3 version with its implicit breaking of backwards compatibility. Backwards compatibility means that there’s a tangle of fragility that only grows with time which is part of why the error messages are so frequently bad. Changes are a fraught proposition. This is part of what inspired my decision to start work on finl.
Probably the biggest mistake was the choice to abandon the idea of having a LaTeX 3 version with its implicit breaking of backwards compatibility. Backwards compatibility means that there’s a tangle of fragility that only grows with time which is part of why the error messages are so frequently bad. Changes are a fraught proposition. This is part of what inspired my decision to start work on finl.