Body Shots are the Problem
Disclaimer: I'm one of the highest rated players in the game with a rating of 2980, but I don't box irl, so take all of this way a grain of salt. This is purely my opinion.
I've seen a lot of complaints about spamming, the damage system, latency, and everything else under the sun, and while many of these are legitimate, I think they are often missing the REAL biggest source of frustration. Body shots are currently massively over-rewarded.
Here's what we know about the current system. A 50 damage shot leads to a stun, whether to the head or body, which causes the receiver of the stun to take 50% more damage for the duration. A knockdown requires 75 damage, so the typical path to that is 2 successive 50+ damage shots. Why does this over-reward body shots you ask? Here's why:
The head is a small, fast moving target. An opponent can quickly and reflexively move it away from an incoming punch. This means it is very difficult to land successive 50+ damage shots against it.
The body is a large, slower moving target. When close together, it can be impossible to move it out of the way faster than a punch can be thrown at it.
Blocking feels inconsistent. Likely due to the imperfections of guessing arm positioning based on hands and head, it feels like punches get through at times which shouldn't. This disproportionately affects body defense, since head movement can mitigate much of the challenge here.
The combination of latency and the choice for client-side hit detection means that we are often fighting shadows of our opponents. This means that precise offense often becomes difficult or impossible at higher pings. This clearly incentivizes attacking the target which is moving the least, since it is much more likely to still be where you are seeing it. That is the body.
The combination of these factors means that at a high level of play, the majority of knockdowns are coming from body shots, rather than head shots, as is more common in real life boxing. This is the real root of the "hook spamming" problem. Players are incentivized to get close enough to rip hooks to the body by any means necessary. So, how do we fix this problem? I have a few ideas, both short and longer term:
Short-term: The quick solution, that I think would improve this significantly, is to decouple the head and body stun threshold, and make body stuns require higher damage. The exact numbers here could be tinkered with, but I feel like 60 would be a good number for the body and you could either leave the head at 50 or maybe even drop it slightly to 40 or 45. This would still encourage body work since it's counting for the same damage, but make players less willing to eat bombs to their head to get close enough to spam the body.
Long-term: I think the longer term solution is to re-think how body damage is rewarded entirely. Body damage is very cumulative in real life (at least as I understand it, I'm not a boxer!), so perhaps taking significant amounts of body damage could make your punches weaker to simulate the physical toll it should be taking. But fundamentally, it needs to be separated from head damage and made less likely to result in a KD or KO.