Oh man. I got really into boxing recently and've been thinking of a game just like this for a while now.
I think you did a great job emulating the strategy that goes into the boxing match as well as feel and flow of it. You clearly have a lot of appreciation for the sport and it shows!
One thing I personally couldn't figured out was how to utilise attack and guard cancels. I assumed it was a reversal/combo tool just like roman cancel in guilty gear, but if it is intended use I could never get the correct timing/proper attack to get any value from it. In general I had some moments where I didn't understand what move beats what, and resorted to mashing. Despite each player having a very limited moveset, the game still feels like there is a lot of potential for outplay and skill exprecion, but it's really hard to figure out. Showing the frame data or even having an indepth tutorial can help with giving all the tools to the hands of the player.
P.S. it would be increadibly cool to give some moves an ability to instantly KO (or just deal a bunch of damage and have a special animation) an opponent on certain counter hits (like if your opponent goes for the heavy punch and you respond with an uppercut), that would spice the game up in my opinion, and bring in some strategies, which are also present in a real boxing matches (do you risk it and go for KO or just deal consistent damage with bodyshots and jabs)
So yeah, sorry for a lenghty comment. I just realised you are already working on the next project, but this is still a gem. Would be glad to see it updated at some point but for now I'll stick to maining hitboxer in Arcus Chroma, I guess lol