The new talent tree revamp is probably the most complex thing they’ve done ingame in a decade, but it’s something they’ve been kicking the can down the road on. The borrowed power systems were basically put in place as a bandaid fix to button/talent bloat issues. Every expansion you would replace 1-2 buttons with a new ability. Just as players it sucked because you were depowered massively each expansion.
Like going into Dragonflight were losing dual legendaries, tier set bonus, and covenant abilities, but they also massively increased the iLvl on the Lvl 70 stuff compared to current season (almost 100 iLvl difference). It’s done deliberately to make sure people aren’t hanging onto old gear in the new raid tiers and also to make you not feel like you’re doing less dps.
The eventuality though is if every new expansion adds more to the talent trees than eventually it’ll become bloated… like 2-4+ expansions from now. Take a look at the WOTLK talent tree compared to classic.