Have you read the articles linked in this thread? They do a good job of showing the negative effects of design decisions in T:A and how they made the game worse.
You can see where one decision like health regeneration being in the game lead to cappers being able to gain too much speed and grab with full health, which lead to them making disk jumps weaker to try to mitigate it, which was a negative consequence because then the rest of the players in the game became less mobile and less able to actually participate in the flag game, which lead to a bandaid fix such as rage and lightweight, which lead to less people being able to participate in the flag game unless you are a specialized chaser or capper with the exact right loadout at the time.
The problem is made worse with poor map design and rock bounces that allow fast back to front routes that are unchaseable by 99.9% of the population. So what do you usually see in games of T:A is maybe a super fast capper and if you are lucky on the opposite team a super skilled chaser that can catch him. The skill ceiling for chasing a capper that can cap in a matter of seconds and touches the ground maybe once is much too high for most people. The other 26 people have given up on being able to chase or take part in the flag game so just end up dueling or d-stacking. People are encouraged to llama grab because of the thrust pack and poor map design like on crossfire where it's much easier to llama down the middle than do an extremely circuitous side to side route.
The weapon balance in the game is terrible. The most powerful weapons such as automatics, hitscan pistols and snipers encourage players to stay on the ground and strafe like they were playing doom instead of skiing, jetting, and going fast. They go completely counter to the vision for the game.
The vehicle design is also terrible. The tank is used as a turret to spam the flag stand on defense and bring the game to a grinding halt instead of an actual assault vehicle. The grav cycle is useless, and the shrike is ridiculously powerful on one hand but also extremely fragile and frustrating on the other. Too much rambling, sorry. You thinking people are just nostalgic for an old game is wrong though =p