Now to be fair, I can see Clone Wars era warmaterial still being as powerful as it is in the game.
It was quite advanced while the Empire's warmachine seems to be built on an cheap budget.
I mean, look at their Mobile Heavy Cannon for instance. The one they built is easily worse than the Umbaran one from nearly three decades prior.
Also when the Empire nationalized the CIS arms industry, they put a lot of people out of work who could probably build, maintain and modify Clone Wars era tech so.
Another thing to note is that the AT-DT is Clone Wars era tech according to Sapanoza, and it makes a mockery out of a lot of other stuff in the game.