I was responsible for a small office, and I tried a bunch of different big-brand expensive prosumer APs, and they all had troubles.

I then tried Unifi gear, which wasn’t as easy to set up, but it worked flawlessly and has done so for years. I’ve since used a few different Ubiquiti products in a few other situations and the gear has just run solidly with zero trouble.

I have used other reliable gear: the Apple Airport was great but now discontinued, every Fritzbox I have dealt with has been fine, and I currently have a Mikrotic at home which has been reliable (albeit in a very undemanding environment). I am about to add a outdoors Ubiquiti AP at home.

Maybe gear is more reliable now, but I recommend Ubiquiti to friends and it hasn’t let me down yet.

And before you say, that you can configure all-in-one to work in bridge mode: yes, some of them. Many of them cannot, or have weird limitations when you do.

I think OP means that you have to be running Unifi somewhere in order to get all the features from the AP. Not that it's just an access point and requires a separate router (which I agree, is a huge plus).

You don't need controller per se to get per-user VLAN assignment or WPA Enterprise. What you need is running RADIUS server somewhere, and controller conveniently provides a basic one (it has FreeRadius underneath, but provides only basic configuration options, so you won't be able to use AD for your users; also do not edit the config manually, any update will wipe your edits).

For guest portal, you need, well, guest portal somewhere. The guest portal is a part of the controller. However, if you need guest portal, I don't see any problem running controller somewhere.

For the rest, you can also run controller on your computer once, configure everything and then shutdown the controller. All the devices will work fine without it.

Edit: word

for the record, most other industry that offer APs that run on standalone will work with all features, or only advertise that feature on the package. For example, you don't see cisco(?) unleashed mode APs advertising guest portal, unless they can do it on unleashed (stand alone) mode.

Unifi is intentionally misleading.