Interesting points
Part of it is the payload maps are too large for 6s, and part of it is you can walk faster than the payload moves so it is somewhat of a chore. In Overwatch payload is liked better because it tracks the payload's exact distance, giving attackers more leniency, with cp you either get none, half, or all of the map, however with payload pushing 3/5 of the map is doable. TF2 doesn't work that way, it instead tracks the points you captured with the cart.
Also the payload carts on overwatch are larger and don't have the glitch network related stutter issues the ones in TF2 do, so being on and around the payload is more pleasant and provides usable high ground.
As for re-spawn waves, overwatch has ults that charge over time and having a changing re-spawn time could potentially loose people games, regardless of that grouping up is important in both games in order for teamplay to work out.
As for the 2cp, alot of the problems overwatch has with it simply don't exist on gorge. In Overwatch while defending, if you loose 2 players in the team fight, you lost first point, respawn times + map length makes it impossible to get back to the point in time to save it on any of the 2cp maps. The inverse is true for the last point. Players from the defending team will be piling onto it during overtime while the attacking team is at a huge disadvantage for reinforcements. There is a character that can build teleporters to solve this issue (Symmetra) but if you run symmetra, you lost the team fight before it started. (even after the buff, your still basically a pyro in a game that has assault rifles).
TF2 cp_gorge doesn't have these issues for several reasons.
1. is engie, he can build infinitely usable teleporters that are easily repaired if destroyed. While he is weaker than a scout, soldier or demo in battle, sentries and dispensers provide your team with enough support to be worth the pick.
2. In general the classes are more self reliant. Your defense won't instantly crumble if glowing-rectangle-shield-man goes down, loosing a medic is somewhat of a big deal but with good plays you still have a change of winning the fight.
3. TF2 doesn't have revives, mass stuns, damage blockers, or unbeatable nanoboosts. All four types of ubercharges have a counter and can be dealt with if prepared. The game isn't a stack of cards that will fall down if you don't kill the healer before the teamfight begins, having a (good) huntsman sniper doesn't mean you miss out on critical utility. Overwatch has so many situations that can turn a winning teamfight into a loosing one in the blink of an eye.
All of these things make 2CP a pain in overwatch. There is no retreat and come back to get the point before it is capped (cp gorge has a long first cap time). There isn't any planning with a spy who can go in an sap the sentry before the push. Every defender is saving their ults for the attacking push and you can be darn sure every attacker is going to ult at the same time when they make their move. Once the fireworks go off the battle is decided in a matter of seconds. Its stressful and feels like you have no control of the situation. Almost like your flipping a going every time.
Overwatch's payload and KOTH modes do not have these problems and that is why players despise the 2cp maps in overwatch. Most of these issues do not apply to TF2, so don't think that 2cp is bad in TF2 just because it is bad in Overwatch.
As a side note, I have yet to investigate the effectiveness of soldier's bard banners on gorge, I plan to do so soon.
TL DR TF2 and cp_gorge gives players more room to recover from their mistakes than overwatch's 2CP maps, thus resulting in a better player experience.