You are in a tough situation.
Wireless isn’t magic, and at the density that you are at Fiber starts to make more sense.
First off, if you have 30 customers on an AP that are on 50-200 Mbps plans I would be hesitant to say that you are actually going to be able to deliver that. The best performance I have seen out of an A5 was above 200 Mbps on a 40 MHz wide channel. (real world, plenty of people with test sites that have pushed the full throughput) So maybe you can do 400-500 Mbps through an AP in your situation, maybe more probably less. I don’t sell Mimosa here, I just help out. I also don’t have a lot of high density deployment experience, so maybe there is something I am missing. (My average customer is +1.5 km from my towers) So I won’t ever say that you should be seeing 1 Gbps through an A5 radio outside of a lab, maybe someone has, but not me. Now, does that mean that Mimosa is crap? No, it just means you need to figure out what your APs are actually capable of and build your network around that.
I would honestly leave your APs where they are and begin moving your high bandwidth customers to either smaller sectors sized APs (RF Elements Horns for example) or 60 GHz. I don’t have a lot of experience with Mikrotik Wireless, though I do know that they have been improving over the last 2 years, honestly you probably made a pretty good decision 5 years ago when you went Mimosa because Mikrotik wireless was in such a bad place. There is also the new Terragraph gear, which while pricey might fit your needs.
From there, you have to have something that gives you an edge over the competition. Where we competed against fiber, we had to really fight. We made sure we had amazing tech support, we built redundancy into our network so we had fewer/shorter down times compared to the fiber company, we were cheaper and we were super reliable with our speeds. (Note: we only oversubscribe our bandwidth 4x which means we know how much our CPE, APs, Routers, backhauls and our upstream providers can do and we will only sell upto 4 times the bandwidth of the weakest link in that chain in an area, most frequently we keep that to even less).
I also implemented a policy of revisiting customer’s issues, when people had issues, we fixed them even if it took us weeks of diagnostics. We then revisited the customer a week or so later and make sure they are happy with the service and everything was fixed. We made it so our customers thought the annoying internet issues they experienced annoyed us more.
Doing all that we were holding our own and frequently growing against the fiber network. It helped a lot that they didn’t have the technical expertise to maintain their network and they had outrageous prices and a boatload of fees. So, it’s doable to compete against fiber, just hard.
I dunno what your prices are or your costs for connectivity, but you might look at seeing if there are better deals you can get. We just dumped one of our upstream providers for another who is selling us 10x the bandwidth for the same cost of our old one.
In short, cut down the number of customers per AP, you don’t need to have 4 radios at each location, build smart and optimize your costs. Have great customer service, don’t sell what you can’t provide and be willing to say “no, I can’t guarantee that I will consistently provide that” people respect you when you stick to your guns and when they run into issues with another provider they frequently will come back to you because of better “service”. Have better uptimes and help out people with technical issues, know your network like the back of your hand and learn everything there is to know about it. All of these have a pretty high cost, but so does fiber.
People are buying an experience of their internet connectivity, most don’t care what the numbers mean as long as they can watch their YouTube videos, Facebook works properly and when they have an issue there is someone who fixes it.