why should I, a certain protagonist, should care about 95% of side quests when I have some dramatic MQ to do?
This is a bit of a bugbear of mine, too many games play fast and loose with their main narrative drive and saddle you up with irrelevant sidequests as you go, and it's a serious conflict that ends up undermining their fiction.
Basically, it's quite common practice for RPG developers to write a strong main plot, typically with dire personal stakes, but then also bolt on a large sandbox around it. On the one hand, this has the benefit of fleshing their world out, making it feel like it's an autonomous, functioning space, but it also has the risk of introducing severe narrative dissonance. An excellent example of this problem is Fallout 4 (though most open-world titles are guilty of it), where you're theoretically on a desperate quest to find Shaun, but in practice you keep taking detours to help some fucknut dirt farmer with his bloatfly problem.
Ideally, when making a plot-driven RPG, you'd want to pace your story progression with natural downtime periods, when maybe you're chasing leads that
might further your urgent goals or you're trying to earn your keep while you're waiting for a previously-concluded thread to bear fruit, thus introducing both the opportunity and excuse to engage with side-content. For instance, Baldur's Gate 2 made a perfunctory attempt at this with demanding you raise a "large" sum in Chapter 2 before you could progress your pursuit of Imoen or Irenicus. It wasn't great, but at least it tried something.
For developers, in a nutshell - pace your narrative urgency and contextualise players' objectives appropriately.