Please explain for me the game damage design

Doesn’t matter the class or the skill…

Why is it a skill with a cap of 5 doesn’t become really useful until you have 20?

So what should be 5/5 is always 20+/5.

My thought is Penitent/T1 should be obtainable with 5/5 max on any skill and 3/3 of any passive. T2-T4 should be push for finding additive to skills and passives, not exceeding 10/5 and 6/3 and all other increases used to push Pits and high level bosses…

Same design has Diablo 2 but poor implementation. In D2 you needed charms with +1 all skills or SOJ or other stuff to make your main damage skills go beyond the limit.