I think the principals of design have been well known for a long time. I think if you are asking the speakers to do some very difficult task maybe new speakers might be able to do it better but for normal listening volumes and materials any good speaker, new or old, is probably fine. The hobby tends to get hung up on scenarios that are largely imaginary or theoretical e.g. nobody over 50 years old can hear 20k tones.
If this is about money then comes the question of what you can get in the new vs. used market. You can buy some pretty nice used stuff depending on what you want. Nobody wants your used floor standers. They come cheap.
The other thing is that there are a lot of great cheap speakers now like some of the Andrew Jones stuff or the KEF Q150. I think that you can put together a really accurate and nice sounding system cheap now and that marginal gains are ever more expensive.
Personally, I feel like room setup and placement is a big deal but nobody likes to talk about it. Cheap DSP, like MiniDSP has come a long way too.
So, in my mind, what's new is there are great cheap speakers that will really do a nice job for short money and you can get some really nice used speakers if you want a form factor that's out of favor. DSP is now so accessible and underutilized.
In the end though it's about being satisfied. I stopped reading forums mostly and dropped out of my audio club because I felt that both things made me unstatisfied with my systems and made me unhappy.
Also, I'll just throw this out there, my wife and I were outside in kind of a pavilion we have with some Dayton outdoor speakers and a chip amp. We were listening and both of us turned to each other and were like "does this sound insanely amazing?" I was checking behind me to see if I had installed extra speakers there or something. It was absolutely amazing. Maybe it was just a nice day and we were outside, but I would put that listening session up against small house money systems I've heard.