One thing that's bothers me the most is that all of them looks the same.

They certainly do not lol

Early on, MC and his friend looked so much alike to me. The only distinction is that MC doesn't emote most of the time while his friend is perpetually anxious

I can see it, I think it's they all kinda got that dead eye stare look. I think that's just this author's style tho when most of us are used to highly stylized manga eyes.