Basically, all you have to do to reach the top is
1: look at random wall/terrain/whatever, it doesnt even matter what it is
2: spam right click
3: repeat
4: reach top
The whole challenge of finding jump glitches and parkour to the top is gone.
This isn't true.
Climbing allows you to right click bricks to "climb" the walls upwards. This allows you to use your surroundings as an advantage over your opponent and find other ways than just using the map builder's way up. This creates creativity in the way you go up. Players learn other player's climb patterns and retaliate with tactics to render these patterns unusable, forcing you to think of other ways to get up. This creates a flow of play that changes regularily as people adapt to other people's movements.
If climbing wasn't there, you would have to:
a. go up the only way via the "builder's path" which will most likely be camped by other players
b. try and corner-glitch up bricks (there aren't that many places for this to be used)