If you learn the maps... you can make them play any way you want.
All 3 of these are no issue to me any more. If you learn your attack routes... you can attack effectively. You can turn Siege into a fast-paced map and really frustrate the campers. Stonehaven offers a lot of cover if you know how to use it. Flooded has a wealth of attack routes.
You have to figure out your plan of action on each map, or you'll just keep being frustrated.
On Stonehaven, just an idea. Use the Overkill perk and take a sniper rifle. Personally, I'd use an AR as my second primary, but you may feel better with an SMG. If you spawn near the castle, stay near the rocks and shadows. If you spawn in the houses area, there's at least one roof you can get on, I think there is a fire in the burned out roof burning. Ideally go there if you can because even with an SR it is hard to see people up there.
If you're atop the house, take a shot then duck out of sight for 10-15 seconds and then ease back up, find another target, take a shot. If you miss, you miss. Don't take a second shot.
As for the Castle side, I'd take a shot and move somewhere else completely. Not super far. But either way, taking a shot and then ducking out forces you to check your six.
Siege, there's a couple of options I like. If you want a lot of action, I think its the north side that's got several tiers of buildings and the south flank that has the tunnel through the hill. Stay on the North side ... but as soon as you score a kill, move back toward your spawn until you can go to another floor level. Just keep moving back and forth like this is what worked pretty good for me. You could also camp just about anywhere on the south flank, the mine side (tunnel, whatever). You'll pick up stragglers but that's about it. You could also run an SR from that area and get a pretty wide view of areas where opponents are trying to cross to different areas of their side of the map. You'll have to be able to get on target pretty fast, though. And getting flanked is ridiculously easy so you have to check your flanks often. Assume any footsteps are opponents.
For Flooded, what worked really well for me was to use Dead Silence and just keep circling the outer edges of the map. Strafe into new zones, don't just go in. In other words, pop half a step in and step back. Any campers usually shoot at the first sight of you and reveal themselves. There's always a second way around them, but if any reveal themselves, you have to crouch walk your way around.
That's what worked for me on those maps.