For me adjency bonuses are a BIG mistake. The last RTS I played was Starcraft2 (before coming back in FA). You can love it, you can hate it but it has one good point: everything is useful. You build a barrack and then put the Reactor addon? It's ok. You put the Tech Lab instead? It's ok too.
There are no "Dead-ends", you can do bad choices on one game but it's your fault because everything is useful in a certain way.
In FA there are many "Dead-ends".
For example adjency bonuses. How many times did you saw noobs putting pgens around mexes? I saw it many times. In fact it's a common mistake, and I'm sure I did it too in my first game. Is it the fault of the player? For me it's more the fault to the game saying "do it it's possible" and giving the possibility to make a bad choice.
It serves nothing...why giving options to do it?
After fixing everything else in FA, adjency need to be completely reworked. We doesn't need to balance it competitively. But at least make it more noob-friendly.
For example mex+pgen could work as a little massfab, less efficient as mex+storage but at least not as useless as now...