Riot seems to have either not enough time to properly address towers, or they seem to be pushing for games to end quickly.
As it stands now, towers fall way too quickly. Prior to the preseason, the first tower fell around 15 minutes on average. Now, i'm lucky if a tower lasts while I back. Especially now that there's a rune that allows tanks with naturally high health (Cho, Mundo, etc) to damage towers really fast. It's becoming an increasingly annoying trend of getting a double kill on bot lane, having the top laner with that rune tp down, and get that first turret within 10 minutes. After this, the game snowballs down, generally ending around the 20 minute mark. I can literally COUNT the number of games I've had that lasted more than 25 minutes on my hands.
This is a problem, but personally I believe riot will address it when they have time. Right now they need to focus on the more pertinent matters, like overall damage being stupidly broken, and which runes are unbalanced and which are (I've only seen maybe 3 people take Inspiration Keystone for anything but Kleptomancy)