ImpStar are said to use a lot of test bed technology (sensors, weapons and reactors are afaik among the things mentioned) and modular assembly line production, which is said not to be that common before them at such a scale and mentioned as one reasons that the Empire can actually build that many. Sure but they still keep innovation and making things more efficient, otherwise they would still be churning out the same ships they did 25000 years ago, which is clearly not the case. One should assume, but the thing that keeps being brought up is that that warships are horrendously expensive, in all areas, from designing, to building and also in maintenance. It’s also said to be pretty much the main limiting factor in Imperial military expansion, because they can easily always recruit more people, but are apparently severely limited in ship building (Imperial Sourcebook), especially with materials flowing into the building of the Death Star. There must be factors limiting it we just have not been told about them specifically, one thing that is brought up quite often though is that they require very specific raw materials that are very rare, which would also explain how they keep having to mine ever remoter planets. It sort of does, as the Dark Empire sourcebook explains, the shield will dampen the Superlaser effect, but part of it will still pass through. The Eclipse also has “conventional” weapons, plus those fun gravity well projectors , which I always wondered about not showing up on the Executor. Though I fully trust Lira to have rushed the design so badly that they couldn’t make it work because of messed up wiring or interference fields.