I've played about 8 games on the new TT since it came out. In an effort to mitigate turtling it seems Riot has pushed it a little too far. I feel like whoever gains the advantage is too easily able to seize upon that and therefore the outcomes are determined far too quickly, even though the game may go on longer. This often occurs within the first five minutes, and the team that has the advantage at the beginning keeps it and eventually wins; this has been consistent with all my games so far. It could be coincidence, but I doubt it.

The only way i've seen to counteract it is to have an AS backdooring yi

I've had a few come-from-behind wins, it's mostly a matter of having a late game team and lasting that long.

I honestly think all of my wins on new TT aside from maybe 1 or 2 of them were comeback wins. I have also had a few losses where the team came back from a rather large gap and secured a win.

I think snowballing is a big issue, and the problem is those relics. Take those out and it's fine.

Also I think game length is also an issue. Games are going on longer than they need to and that's because of the respawn timer. They said they reduced it, I think they reduced it a bit to much. You ace a team and have just enough time to push one tower.

The relics encourage snowballing like crazy, it's definitely possible to make a comeback victory, but it's much, much harder than it should be after a team gains even a small advantage.

The fact that the relics provide a percentage-based bonus rather than a flat amount based on your current level or length of the game is a problem too. If one team has a sizable gold advantage over the other, and the losing team manages to win a teamfight and they take control of both relics, it's going to be far less of an advantage for them than it is for the other team, because they don't have as much AD or AP to boost with the 10% bonus, even though they have to work so hard to get control back.

Then again, even if it was a flat bonus, there's still much easier and more of an incentive for the winning team to hold control over both relics, so I guess it doesn't matter too much. Maybe the point of the new TT is to let one team snowball and end the game fast? If it is, then the relics are fine, but if they're looking to create a balanced map that might see play in tournaments, then they definitely need to change them.

I think, the main problem is that there isn't anything you can do to come back. You can only sit in your base wait for some really dumb mistake of enemies. Like going in 1vs3 or tower dive. I mean fountain dive, cause normal towers are useless.
And if they don't do any mistakes, they keep snowballing more and more, until their Singed or Darius is fed enough to laugh at towers and ace you in your base.