Well, the combat system for M2TW cannot be changed back to how it was before as that would be a fundamental change. IIRC fights between men in previous TW games involved the two meeting and then the usual attack defence calculations taking place. I'm not sure how this works, but it may be based on "attack rounds" or some such system. The M2TW system sees the combat based on the animations themselves. So a weapon is literally swung and hits or misses an enemy. In previous titles the swings and thrusts were cosmetic. This new system introduced a lot of bugs where certain units could not hit other units due to the types of swing etc. This has been addressed in patches but not fully resolved AFAIK.

RTW does not have this system so you can work with it and improve it somewhat through modding, but it still falls short due to pathetic battlefield AI and numerous bugs, especially pathfinding bugs in sieges. Unit movement rate, kill rate and other factors such as morale, fatigue, height and weather are also messed up in RTW. It's very much shock and rout tactics and battles are all over in a matter of minutes. Some mods address this but I've yet to see any mod that has fixed all of these issues.

The fact still remains, that if you want to play the tactical battles you don't have much choice. STW and MTW are still the best there is.