I know this dates back to Insurgency 1, but it's very annoying and has devastating potential. Some maps are better than others, obviously, but it's still a problem that requires a response. I suggest limiting the defender's zone out past their objective more. To elaborate, defenders can almost push right into attacker's spawn before the level cuts them off. That cutoff needs to be closer to the objective, not Attacker's spawn.
I would've jotted down the name of the map to help, but I just played a match on a map where Insurgents attack. We spawn and we could run down a long street or cut through some buildings to get to A; however, there are two roads that split these: Defenders can easily camp on them with LMGs or marksman and will cut down wave after wave of Insurgents, and are difficult to flank. One of the roads is right next to Insurgent's spawn, and with the right player, can severely limit the Insurgent's ability to leave their spawn untouched. Defenders won both rounds.
It really takes away from the competitiveness of the game, and can turn even the most evenly balanced of matches into a one-sided affair. It's not 100% of the time, nor does it work 100% of the time, but it's still an option to defenders, and it still ruins games when it happens. Nothing else I've seen so far has this potential. A good choke point is encouraged and accepted, but not right outside of Attacker's spawn, please.
Thank you for your time.