blazing jetty
You see it all the time on maps like river, construction, sandy, and frugis. Even Kodiak and zalfi have this problem. One group can hold an entire building until it comes down so long as one or two get to the top floor and blow out the stairs. Or if the building isn't one that can collapse, essentially forever. Bad enough on off point buildings, but if you're playing a map like construction and those buildings are the points, it gets much worse as you can't even jury rig a staircase with buildables anymore.
And I get that the grappling hook is a thing, but it is very limited use, leaves you completely defenseless until you've climbed the whole way, and is only available on assault and recon(by forgoing other, much more generally useful gadgets.)