The level of amp seems to provide diminishing returns as you go for the final 1-2% of tone. Sort of like building a performance car. You can get a lot for a little, but a little more cost a lot. Bad analogy?
Pretty good high level analogy to me, makes sense yes; I have to confess I do love motorsports, especially classics (do we see a trend there?), so that speaks to me.
I'm sure one could think of similar phenomenon in lots of hobbies/passions/domains of interest, whether those involve "technics", technology, or just endless pursuit of improvement. "Perfection", or simply "better", is often an asymptote, trying to reach it never quite ends.
I would just ad that in this particular "personal quest" for "the tone in our head", there is no real absolute "better" in ways/tools to reach it IMHO; and amps are no different in that VS guitars, or whatever other part of the "rig".
Once you reach a point, it's much more about "different", "flavors" etc. VS one particular taste, environment, contraints, history of learning/playing...
The trick is pairing the right amp with the right speaker.
That is for sure one of the key "tricks" you learn with experience, in that endless "quest".
One of the keys to help progressing in that quest is about having strong stable references to me, so that you have "starting points" to go from; Once you find something you like a lot, that "feels special", you can use that to find tune thinking about which particular fine detail you want to adjust and in which direction.
And I feel that when you think you found an amp+cab/speaker combination you feel like being 98% there, it may be time to go back to adjusting something else and leave those alone (to relate to the fact speaker/cab changes can quickly have such major impact).