I joined right when Season 3 started. You want to know why it was so good?
- No Yasuo
- Jungler was optional (duo top was the norm, after season 3 ended junglers were a thing for good so we can have level 2 rengar's diving level 6 rivens at half health and ruining your game!)
- Team Builder (guaranteed champ and role, pick who you want on the team, kick out people you don't want) began its three year, way too short existence.
- Patches didn't come out every two weeks so people actually got to play champions without nerfing/buffing/changing everything about them constantly.
- Most people were a lot nicer than our lovely community today. People would help newbies out, now most newbies are just smurfs trolling on a new account.
- Nobody dreaded the incoming reworks to their champions which Riot had so much confidence in they refuse to offer refunds once the champion is announced as being reworked, since at this point the champions were still all relatively newish.
Now today, everything gets changed constantly and we have Yasuo running around with nearly no cooldown destroying people thinking he's actually skilled, and right next to him is true damage assassin Yi with a meditate that pauses his ult and E while he stacks double-strike, builds being generally static like you said, champions being changed significantly every two weeks, and team builder being gone for the failure that is champ select which actually is WORSE than a mode added four years ago for champion and role guarantees.