It's just that aircraft have it relatively easy to camp a spawn. I feel it's gradually changing though, more and more burstersmaxes are popping up, especially near spawnpoints. This is a great deterrent for the light aircraft podders.
Besides if the enemy has gotten to the point they can surround the spawn they have pretty much conquered the facility.
I still prefer the base fights of ps1.
Ground vehicles and aircraft are useful inbetween bases and to push into the courtyard, but to actually get to the objective(spawn/generator/control consoles/llu) you need infantry to go into enclosed/underground areas.
With about 3-5ish ways of entering the infantry-only areas and a decent number of choke points (usually with a few alternative routes) and open areas you'd see quite a bit of fighting even when the attackers had superior numbers. On some base layouts it could drag on for a bit but after a while the base would run out of fuel unless the defenders manage to secure the courtyard long enough to bring replacements.
The base walls were also a lot more effective at keeping attackers outside so that interesting fights happend around bases, within the courtyard and inside. The base lattice provided structure to how frontlines formed and in which order stuff got attacked.
Instead bases in ps2 come with a silly number of vulnerable objectives each with more ways of entering than a typical ps1 base. Most of the rooms housing an objective (if it even is inside) will have some open spot in every direction so its always possible to get shot in the back while trying to defend that spot. Nice...
Some of the capture points in ps2 can actually be taken by driving up to them in a tank and parking there. I even managed to drive a lightning right next to the "A" control terminal room in one of the aircraft tower bases on indar.
There also was way more space between bases for battles to occur, where as in ps2 you can see/shoot into adjacent bases easily. It was easy to fly around for a few minutes without getting close to any base. In ps2 you cant avoid running into them not to mention that you run off the map within what feels like 2 minutes.