Then there is a balance patch and all the builds you once knew are different and you have to play different

I definitely found that to be the case in AoE4, and to a lesser extent in AoM, but never in AoE2. I think partly it has to do with how mature the game and its balance are. When they get to a stage where fewer big changes are being introduced at once, older builds are probably still viable.

I think it can also be easy to get caught up watching the pros' "Patch X Civ Y build order" videos, thinking you have to watch and follow the latest patch's BO, when really this BO is often just an extra option on top of BOs that worked in the previous patch and still can work. But the pros gotta put out that content to appease the algorithm.