All mechanical problems are not that difficult to solve, IMHO, the mayor hurdle remaining for FDM is the materials used to print, there's no perfect (or reasonably satisfactory) choice.

PLA is close to perfect in terms of printing, extrudes easily, no need for a heated bed, very little shrinkage, very good layer adhesion, but... it doesn't have good stability, it deforms over time under load and at relatively low temperatures (60C) it turns to bubblegum.
Besides that there are two other important advantages to PLA, first that it is not based on fossil fuels but renewable sources and second that it doesn't emit toxic fumes as most other filaments when printing, which makes it much more suitable for home use.

ABS prints quite easily, has good mechanical properties but requires a heated bed and that's not even enough to solve the big issues with shrinkage it suffers from, specially since layer adhesion is much poorer than PLA leading to delamination of the layers.

I've tried HIPS, it is similar to PLA but without the deformation and low temperature issues, however it has even weaker interlayer adhesion than ABS.

Nylon and PET are, AFAIK, the strongest materials, with great dimensional stability and interlayer adhesion but... you can't glue anything to them, in particular Nylon, which limits their use , for example I use 3D printing for airmodels, and not being able to glue some pieces together is a no starter.

IMHO a PLA with higher glass transition temperature and mechanical stability would be the Holy Grail of FDM