I very much agree with the assessment on target-agnostic damage, and its similarities to GW. Specific counter-mechanics like these tend to distort balance around them and make it very unstable when they're not involved. It's kind of like pressing on the accelerator and the brakes at the same time, where in the end you achieve very much the same result as if you weren't doing it, but in doing so you also increase stress and instability overall. At this point, target-agnostic damage is on almost every new or recently updated champion, and tanks have been balanced around this, so whenever they're tough, they feel unkillable to champions who don't innately have anti-tank mechanics.
I also agree that it's been a gradual process, though I also feel it's a pretty good cautionary tale against feature creep. Over time, Riot gave newer designs features like target-agnostic damage, crowd control, utility, and so on, not because it was core to the champion or their functionality, but because they wanted the champion to be able to contribute even when behind. Because this reasoning can apply to literally any champion, it has been overused to the point where having a slow or a percent health nuke really isn't special anymore, and champions have to be loaded just to be able to compete. Features like target-agnostic damage have become part of an arms race in champion designs, and as a result it has also both constricted design and destabilized balance. It's also part of what's caused fights to become too fast-paced, I feel, as target-agnostic damage means tanks die due to nukes ignoring their durability and bursting them down quicker as a result, rather than, say, DPS or some other kind of persistent pressure whittling them down.
To a large extent, I also agree that I'd prefer the tankiness of tanks to be more active, rather than pushed to base stats. Any kind of power put into base stats means power taken away from abilities, and in many cases that has left certain champions with less agency than they deserve to have. Taken to extremes, I'd much prefer a game where tanky champions had squishy health pools, but also abilities that gave them extra health bars' worth of shields, heals, invulnerability, etc., than one where the durability of tanks were completely passive, which is almost entirely the case for many tanks right now.
On the subject of snowballing, the issue I take with it isn't so much that it accelerates the end of the game (this is good, and to some extent necessary), but that snowballing in League means champions end up out-statting each other pretty hard. I think fights should always be entirely about skill, no matter how far ahead one side is relative to the other, and any kind of stat lead compromises that. It also leads to certain situations where champions cannot contribute or function at all if they're too far behind, or have little to no counterplay when ahead, which forces them to be loaded with additional mechanics as a result.
To me, the most fundamental aspect of any kind of lead in a MOBA is that you get closer to destroying the enemy's base: because of this, I think the most direct way of expressing any kind of lead should be damage to structures. However, League rewards leads primarily by making champions more powerful, and only then do they turn that into an advantage that speeds up the pace of the game by attacking turrets. In the meantime, though, it means that they're also expected to win fights increasingly more often, and it's this aspect of snowballing that tends to ruin matches, both by making them feel unwinnable to the defenders, and unchallenging to those who are ahead. Because these leads don't even directly lead to the destruction of the Nexus, they also have to be accompanied by really heavy-handed systemic changes, such as tremendously snowbally stat leads and massively weak structures, just so that games can increase in pace. It's because of this that I'm apprehensive about adding more snowballing to the game, at least in a way that depends on stats and items.