The question is not whether max speed is the same for more people, which it obviously is not. What I don't know if the number of devices alone, even when idle, kills your bandwith.
I've noticed our office Wi-Fi is rather slow and the explanation from IT is that there are so many smartphones etc. However most of the time most of them are not actually downloading anything. All the computers are using wired ethernet. Access points are properly managed with non-conflicting bands as far as I can tell.
So will you get worse downloads with access points supporting 20 devices as opposed to 2 even if the other connected devices are not doing anything? Does it depend on the tech ie 802.11 g/n/ac?
I tried searching, failed. And to be clear, this is not about a real network problem but more of a “how things work” type of question. In this case, very specifically about the number of passive—yet still connected— devices present degrading the performance of any active device(s).