However, I wouldn't consider gear, rules and ring minor.
The improvement in sparring gear has allowed us to do a lot more than before with a greater degree of safety. Also advances in medicine are a major factor - just imagine what most of the pro MMA fighters might look like using pre-WWI medical methods. The rules are incredibly important and something that a lot of armchair martial artists totally overlook. These define the sport and any athlete or coach worth their salt knows how to play into them. And of course, the ring is a huge factor. Even Sunzi talked about the terrain. It's a completely different environment when dealing with a leitai vs. a cage vs. ropes & turnbuckles. But all that being said, fighting probably hasn't changed that much as human bodies haven't changed that much (we'll overlook performance enhancers by filing that in with medical advancements
), so the core is the same, just the terms might have changed.