Strategies evolved over years in Warband, but they're pretty stagnant for Bannerlord. This could be because competitive-minded people aren't sticking to Bannerlord as much as they did in Warband, or because of existing class/mechanic/game mode imbalances, or just general lack of popularity. Changing game modes is a one-off way to force a change in strategy, but new metas in popular games are picked up fairly quickly at the top end after balance passes or overhauls. We're not seeing much in the way of iterative meta development in Bannerlord.
It's a shame, really, that the people who had been dying to push the envelope are so disillusioned with the game and its progress that they've abandoned it.