Are skill/support gem levels needed?

My interest in this game is experimenting with builds and engaging with the enemies and bosses. Time spent in menus or failing to understand mechanics is time lost.

I don't understand why skill gems are in this game.
Gem Limits:
player level
gem level
support gem level
support gem stat requirements
skill cap of 10
2 support gem limit per skill
weapon

If you remove gem levels you still have 5 limiting factors.

Are skill gem levels necessary? Why can't I just have a stack of skill gems and support gems? Why can't I just have skill points to assign to gem slots? Just gate the support gems with character level instead of support gem levels dropping at a certain player level.

Why does the game need level 4 skill gems? I need level 10 to use them, meet an attribute requirement depending on skill type and level, have the appropriate weapon, and have the level 4 uncut gem itself. The question is: do you want to attract players that want to engage with the combat and environments, or players that want to pour over every skill trying to figure out which to change from 3 to 4, only to discover that level 5 is the big jump for skill gems anyway? Why don't I just throw level 2 and 4 skill gems back on the ground?

Why can't I simply "socket" any 10 skills I want as they are already gated by level and weapon until I find the ones I want to use? You want to give one uncut skill gem point per 2 levels, that works for me.

And what if I pick a support skill I don't like? Why can't I just extract the cut support skill gem, socket it into a new support skill, and get back into battle to figure out if it works?