I'm not advocating one way or the other, just wanted to point out that TML is one of the potential rewards when going for an early t2 com, and since it threatens such a large circle, it is the primary threat if one manages to gain mid map control early on ~10km maps or to do a t2 drop on 20km.
It's worth noting that TMD is one of the very few defensive buildings you usually see built preemptively by veterans, only other I can think of that comes close is a shield over your t2 power. All other threats in the game are better countered by units, not static emplacements, or afford defenders enough time to respond if the scouting is on point.
What would change if they were removed? I think, in some team games, guncom + spam would get a relative buff compared to t2com + fire base. I also agree with your premise, noobs would have an easier time overall, and while this can be said of any simplification brought to the game, this change would make a bigger difference than most for noobs