Is it my imagination, or did Fighters from previous eras generally fight at a faster tempo? Say, maybe up until around the 90s or so? I'm not talking about the actual amount of punches thrown, but a sort of faster paced type of thing.
I don't think so, no, but feinting is tactical now, not strategic, that's a fact I say. Motion as a protection against predictability is by the by, mostly, but more than that a long-lead feint is now a very rare thing, which is natural as fights have got shorter. Far less point in hiding a punch or selling a tell now than ever before - in fact, if things go wrong strategically say over four rounds, a fighter is basically in a hole he can't climb out of (or nearly). Guys still use individual feints to unlock doors as standard, but it's only at the very top of the fight game that you see elite long-lead trickery of this sort. I think what lends itself to the feeling that fights were higher paced is the reluctance of the referee to be involved the further back you go. So relentless maybe but faster no.
I think with 15-round title fights (and 20s before that in some cases), you’d often see a more slow-and-steady-wins-the-race approach in the first 10 rounds. True 15-round masters like Alexis Arguello would often work the first 10 rounds to set up for the championship-round sprint to the finish, increasing pace and workrate once they got past 10 and their opponent was a bit ore spent.