Yes, the 2.4 GHz WiFi band is getting more and more crowded. There are several issues that you may be dealing with. I will list them and then explain each in more detail (warning, this may get long).
- Channel crowding on the 2.4 GHz WiFi band.
- Client capacity of each WiFi access point.
- Capacity of DHCP server.
- Subnet size.
There are others, but this is the short list.
Starting off with channel crowding on the 2.4 GHz WiFi band. Yes, the vast majority of IoT devices operate on the 2.4 GHz band. Some also work on 5 GHz. This discussion is based entirely on the rules in the USA. If you are another country, the rules may be different. The 2.4 GHz WiFi band has 14 separate channels, however only 11 of them are legal in the USA - channels 1 to 11. These 11 channels are spaced 5 MHz apart starting at 2412 MHz and going up from there. When a channel is used in most cases it uses an occupied bandwidth of either 20 or 22 MHz, so for example a signal on channel 1 at 2412 MHz actually occupies 2401 - 2423 MHz. That means that the channels overlap (more of that later). All WiFi operates in what is sometimes called a squirt, squirt mode. What that means is that one radio transmits for a short while and then then the other radio transmits for a while - on the same frequency. This is repeated many times per second. As more and more devices share the channel, the radios have to wait for other devices that are transmitting. That slows down the ability to transmit and therefore the data speed. Because the channels overlap, not only does your radio have to deal with other devices on the same channel, but also on devices on the nearby channels. The less overlap, the less of a problem. You may have heard channels 1, 6, and 11 as clear channels. That is NOT correct. Those are the only three channels that allow three channels at a location that don’t overlap with each other, but they do overlap with other channels. Channel 1 overlaps with channels 2 - 5. Channel 6 overlaps with channels 2 - 5 and 7 - 10, and channel 11 overlaps with channels 7 - 10. A lot of people use one of those three channels, so you are often better to use the in between channels in a congested environment. Some newer technologies use 40 MHz wide channels, so there is even more overlap.
Next up is client capacity of your access point. All A/Ps have a limit as to how many devices can connect to it. For a lot of consumer A/Ps, that limit is fairly small - a few dozen. Some high grade commercial A/Ps can handle hundreds of connections. If more devices attempt to connect, any additional connection attempts will either fail, or bump an existing connection off of the A/P. In most cases, you have no control of this limit other than replacing the A/P. BTW, generally that limit is NOT documented in the consumer documentation. Sometimes you can find it with serious research, and sometimes not.
Just as your access point has a hard limit to the number of connections, so does your DHCP server. The DHCP server is the device that issues IP addresses. In most consumer equipment, the DHCP server is part of their router. In most cases, the DHCP server is less restrictive than the access point, but it CAN be configured to be highly restrictive.
The last one I will touch on is subnet size (referred to by subnet mask at times). The vast majority of consumer routers default to a subnet mask of 255.255.255.0 which results in 253 available IP addresses for connected devices. Again, usually not a limit for most of us. However, it can be set with a smaller network size.
As for how to fix the 2.4 GHz problem, there are a couple possibilities. The easiest is to set up an additional access point (not a router, just an A/P) on the same LAN on a different channel. For example have a north side of the house A/P on channel 3 and a south side of the house A/P on channel 9 - with different SSIDs. Cameras are set up to connect to whichever A/P has the best signal (generally that means the closest one). This will spread out the channel loading between the two (or more) A/Ps. SOME WiFi mesh systems are smart enough to do this, but very few. I am not aware of any A/Ps that will simultaneously operate on multiple channels on one band (I’m not counting mesh devices that link on a different channel than is used for user connections).
Moving devices that are capable of 5 GHz operation of course completely removes them from the 2.4 GHz problem. For example, my Amazon Echo devices all connect on 5 GHz as do all the phones. But they are capable of 5 GHz. None of my IoT devices (Wyze and otherwise) operate on 5 GHz.