I know it's most likely a beginner question but it's what I am I suppose.

For extra context, I generally have about 6-10 hours to spend to game per week and I find I do enjoy the main quest but after spending a couple days only doing that it feels like I'm missing out by ignoring some of the side quests.

I only have 1 charachter so far and it's lvl35 at around the start of ACT2.

Will I lose out on powerlevel if I just try to get through the main quest first for now and look into doing sidequests afterwards? Am I making my life harder if I do sidequests first?

Right now I think I would like to be able to participate in the seasonal with a new class to try out, since it is still an expensive game and I want to feel like I experience more than just one class.