Native maps are pretty bad mostly. They offer a lot of camping potential and some of them are clearly designed for 64 players max. Besides, gravely overplayed and not actually that well made. Port Assault and Nord Town for example, are horrible camp maps. Battle on Ice as well, there is always people hiding in the woods, really bad sloping, all these maps are way too small as well for a 100 players. Bridge maps are not at all unbalanced per definition, actually bridge maps are often very balanced. They usually do not offer very fun gameplay though, that I agree on.
Some of them have very bad optimization (i.e. a lot of unnecessary details which is completely unprofessional - you turn around at 360 degrees and there are some parts which make your fps drop to 70).
Sadly mappers are not professionals. They are people that are willing to spend a lot of time to create maps for free for this community, and I dare say maps are quite important in this game. Creating an optimized map is extremely difficult, as you have no idea how it will run with loads of players on. Especially if you do not have a bad pc yourself it is really hard to estimate how far you can go before people with crud pc's start to suffer. Furthermore I think there is still quite little insight in what actually hampers performance, the do's and don't's for a smooth running map. I can speak out of my own experience that you are basically clueless to when performance gets bad
A big problem is that map updates are far and in between. I for example also released a map, which somehow has a wrong spawnpoint, which I could have sworn I fixed before. The first time I played it, I fixed it for sure now and reuploaded. That was two weeks a go and still the map is fucked in the rotation and quite unbalanced because of it. Same with performance fixes, they just get updated very slowly if at all.
In any case, if you want to make the map rotation better, make maps yourself. Or provide map specific feedback with clear arguments why a map is bad. I would take screenshots because all the map names are fucked up. Saying 'map rotation is bad, make it better' or 'That one city map is shit' does not really help. If you want a mapper to change something, provide him constructive feedback in his thread.