The first thing to consider is what genre you want to model. What kind of fiction you want your game to look like.
Then choose the game system and the adventures you use with it to fit the desired style.
If you create a situation where there are important things to be done, don't expect the characters to take downtime until they complete them. Divide the story into arcs with fast action, separated by long intervals with no tension and no big goals to pursue. The arcs may be as short as a single game session, or as long as several levels.
This won't work with most published adventure paths. You need to prepare your own adventures, or modify the modules in such a way that they fit the arc-downtime-arc structure.
If you don't want to insert downtime this way, I don't think there is any good solution. You either need to accept D&D fast advancement, of switch to a game that has much slower one.
Then choose the game system and the adventures you use with it to fit the desired style.
If you create a situation where there are important things to be done, don't expect the characters to take downtime until they complete them. Divide the story into arcs with fast action, separated by long intervals with no tension and no big goals to pursue. The arcs may be as short as a single game session, or as long as several levels.
This won't work with most published adventure paths. You need to prepare your own adventures, or modify the modules in such a way that they fit the arc-downtime-arc structure.
If you don't want to insert downtime this way, I don't think there is any good solution. You either need to accept D&D fast advancement, of switch to a game that has much slower one.