As an avid sci-fi reader for 40+ years, and wanna be writer, I've wasted many hours thinking about space battles. My conclusion is, massive fleets doing battle is unlikely because it will just be too damn expensive. I Iove stories about fleets of ships, from the biggest capital ships down to swarms of fighters, but now I'm starting to think, when yet another battleship explodes like the Death Star, damn that was a lot of money.
I read one story where a planet was wiped out using sand. Granted it was a LOT of sand accelerated to nearly the speed of light but it points out that something very small, going very fast, is a potent weapon. Just look at today's headlines where a few dollars of diesel and fertilizer are destroying much more expensive things. Could any economy support the construction and destruction of such expensive toys? Personally I think such massive fleet actions will remain the stuff of science fiction.
Putting the economic arguments against such things aside, I'm an advocate of the right tool for the job school of thinking. Which just means there will be all kinds of weapons in play. Someone building mirror coated ships means someone else will invent a hammer throwing gun. Either way, someone is in for some bad luck.