The timer for surrender should be increased to 25 or 30 minutes again.

during the 20-th minute one team or the other gets ganked heavilly and leads to one team surrendering and ruining most games before they get to the team fights , part of the game. and as such, ruining the game.

One of the most challenging and for me personally the reason why i play this game, is the part of the game where one team is seriously down and its players are doing all their cordination and all the teamplay with one purpose, turning the flow of the game around. And we dont see that anymore. 9/10 recorded games i have currently ended at 20-25 minutes with surrender. none of which even got to the team fights.

Even when the surrender was available at 25 min i found surrendering because one person in the enemy team got fed very disruptive, but it only got worse with the decrease at 20 minutes.
if nothing else let the requirement for surrender below the 30 minutes mark to be triggered with 100% agreement of the team, and to be reduced to 70% past the 30 minute mark. i believe this will be the good middle ground for teams that want the game to end and teams that are just having a single bad gank.