The REAL reason why waveclear mid meta arose, and why people want assassins back

Jungle. Junglers are so overpowered that they can simply build or be and have farm equivalent to a laner while clearing extremely fast. And as a laner, you cannot contest a jungler's farm at any point of the game due to the existence of and you will be collapsed on by a minimum of 2 people on the enemy team. The only player that can contest a jungler is another jungler, there is absolutely no counterplay from a laner perspective. Yes, you can avoid ganks and play safe, but that's not really counterplay. If the enemy jungler forces you to play safe, they've done their job as it lets their laner free farm and have an opportunity to roam. Alternatively, they can just pick a scaling jungler, free farm, and be allowed to duel everyone in the game which is why was broken earlier this season. Also coupled with the fact that they have complete objective control provided they're competent because you can't outsmite them unless you are a or a lane and if your jungler is underleveled, your team straight up cannot contest baron/dragon unless your team is significantly stronger as a whole.

Now you may ask, where does the waveclear meta come into play? Because junglers clear very fast and achieve uncontestable laner farm, it disincentivizes solo killing because the moment you try to go for a solo kill, the jungler could show and fuck your shit up and you cannot fight back because they are the same level as you + the existence of the shit design that is challenging smite combined with red buff. It doesn't matter if you warded, with the removal of buyable green wards, it's impossible to have all sides warded, so if they just so happen to gank from the unwarded side, you straight up just lost the lane. Bonus points if the enemy jungler pink wards your lane to camp it while your jungler just afks in the jungle or ganks another lane. So the obvious and logical conclusion to this is to just pick strong waveclear champs, so that you secure your farm as fast as possible, shorten the window enemy jungle influence, and give yourself the opportunity to roam. There's no reason to try to 1v1 your lane opponent which can be easily met with jungler resistance when you can just waveclear from a safe distance and let yourself scale off of farm. Coupled with the nerfs to assassins over the years, they can no longer 100-0 you at level 6 extremely quickly if you misstepped.

And this brings me to my next point, the reason why jungle didn't seem that big of a problem in past seasons was due to the fact that assassins were very strong at this time(think s3-s5) which after this point also marked the start of League's decline. Assassins at this point in time didn't have delayed burst which meant that they could kill their laners very quickly if they were good, so fast that by the time the enemy jungler came out of the river/tribush, the assassin had already killed their lane opponent and were on the run. Even if they were not going for a solo kill, assassins had the mobility to escape ganks and effectively canceled out jungle influence. With their burst and mobility, they could also roam, so even if your jungler was complete trash, you could disregard such a player and snowballed off of other lanes very hard. This is the main reason why was considered by many to be broken and overpowered, because she had the burst of an assassin back in S3 while also having the range and safety of a meta waveclear champ today, and she could also roam if she picked up TP with her W. And because snowball was very strong in the past, with 3 kills or so, you could effectively start 1v2ing your laner and the enemy jungler. While obviously we know now that snowballing was horribly balanced in the past because you straight up just lost the game if you died twice to something like a Riven who could 1v5 with enough items, it was masking an even worse problem by design that is jungle.

Jungle has no counterplay as a laner, and the only time jungle is ever a "bad" role is when it's overshadowed by overtuned burst champs and snowball mechanics. In order to give back laners the solo carry potential we all remember while still keeping the counteplay of assassins relatively balanced, jungle HAS to be reworked to have significantly less influence in the early game (a good idea of what this would be like is the way jungle works in Dota, farming is significantly slower in the early levels, so slow that you don't have any opportunity to gank in the first 10 minutes, and it ramps up later in the game so that you can still scale just as hard as a laner) , in order to give people incentive to actually try to kill their lane opponent. Because right now, the risk of trying to kill your lane opponent and try to snowball far outweighs the possible reward. And honestly, no one likes junglers, not even junglers themselves, so there would be no loss if jungle got nerfed to be more in line with other roles.

TL;DR Jungle influence is what's killing solo carry potential and solo killing in lanes, waveclear meta arose in response to this, and is what I believe to be the main reason why League is declining, and the role needs to be reworked if Riot wants to make their game enjoyable again.