If you want to play the pentagon-challenge then esp. in Africa, CONCACAF and in part in Asia it is imo very beneficial to have much more leagues loaded, because the competition about the international club trophies gets harder. And you start unemployed, with no coaching badges. So if you get your first job in CONCACAF for example, you most definitely will not manage a club in Mexico, USA, Honduras or Canada, which are the most likely to get you relatively fast to glory. Same goes for all other continents. And you still have the option to reduce leagues, although my goal would be not to. It´s not just about the practical side of things, rather its a somewhat irrational love for the game. Sometimes I can get lost for two hours watching stadium-pics of some obscure league (of course with graphic-addons). So the more information in my football-world is available the better for me. And I am more than willing to have longer loading times for that.
Still - there is the question if it gets to slow after xx years and if yes, when this will happen. If after 30 years my loading times for a week are 10 min or smth I would completely go with that. Like I mentioned - I dont mind the waiting. Unfortunatly I have no long term experience with such a large setup - hence the question.