I still really feel like nerfing jungle spawn timers snowballed into bigger issues.

When Riot made it so camp spawn timers were a lot less, it encouraged junglers to gank with no oppertunity cost.

What do I mean by this? I remember before, everytime a jungler decided to gank - every second they spent pressuring a lane - had a small oppertunity cost - in how much xp/gold they would be missing out on camps. A bunch of failed ganks would mean

Disclaimer: I do not believe the devourer had a healthy playstyle, but it got removed before the jungle changes.

This meant that ganks had to be fast and efficient. And it wasn't like junglers with faster clears got "more gank time", because even the fastest clearers could rarely clear before their first camp respawned - meaning there was still an oppertunity cost. Every ~15-30 seconds you spent looking for a gank, was cost of around 70 gold and xp.

So what are a few consequences of this?

Lowered Solo Carry potential: Especially mid lane. It became FAR, FAR, FAR too risky to actually pressure mid lane in a winning matchup. Because chances are, you get ganked within 10 seconds. Also, its not like if you avoid 2-3 ganks, you put the enemy jungler behind - they can just keep coming back mid. I remember in S6 the meta was that mid laners would literally wail at the enemy's tower if they were ahead. I remember back when Faker would solo get first tower mid every game.

This suddenly evolved the meta into the "push and roam style". It was far too risky to stay pushed up in lane - so what better way to use your winning matchup than just roam? This pretty much doubly fucked bot lane/top lane - because now you have to deal with a jungler free to gank, and a mid laner free to gank as well.

Before, in all 3 lanes, you had more time to actually press your advantage 1v1 or 2v2. Now, you expect to get ganked almost instantly. And the only thing left to do is blame your jungler, because at least before you'd be like, "hey, maybe I'm getting camped, but my jungler is up like 2 levels". But that really isn't the case anymore.

TL;DR: Changing jungle spawn timers kind of just destroyed the concept of laning phase. This is probably one of the biggest reasons people think "solo carry" is out of the game.