Smurfs and account sharing

Why can't riot implement a way to prevent smurfs and account sharing better? This never is addressed and it ruins the game for new and low elo players. I'm silver and I can't enjoy ranked because of smurfs, and I can't enjoy normals because it pairs me with plat 2 and 3 players on the other team.

Smurfs and account sharing make this game unplayable in any way shape or form. It's un fun to play against people 3 and 4 Leagues above you. It happens in at least 50% of my games.

The person stomps hard with their fresh lvl 30 account, or their bronze/iron 3 account and half the time they reveal their d2 or d3 smurf OR they are helping a friend out.

In the years I've played this game (7) i've spent way too much money and i'm done spending a single penny until this gets addressed.