As the Iraq and Afghanistan wars recede in the past US and allied forces will not be as experienced in actual combat.
At the other end of the scale China has only the Korean War and its unsuccessful invasion of Vietnam to drawn on.
Combat experience does not seem to have helped Russia to fight in Ukraine.
So the relevance of actual combat seems to be variable.
Combat experience is always useful. Not sure recent Russian experience was useful in preparing for a near-peer conflict though. The same could be said for post Iraq 1991 conflicts for the West as well.
Whether the right lessons are learned from combat experience is less certain, and different militaries (and societies) may differ in how honest they are in self-reflection.
I suspect that combat experience is only useful when the military leadership is sufficiently self-critical and sufficiently professional to change when their existing practices are found to be unworkable. A case in point is the French Army in WW1 which remained tied to tactics which led to massive casualties and large-scale demoralization far after a more introspective (and, in my opinion, professional) military leadership would have changed.
Everybody learns from experience (except those for whom the experience was terminal). Smart people learn from others' experience. One would hope that the various pro-democracy armed forces are paying attention to what's happening in Ukraine, both in what Ukraine is doing right, but also to what Russia is doing wrong. One can learn more from failure than success.