The issue is the ambuguity in what someone intends when they just say radiation. It is valid to call any electromagnetic wave radiation. However, as for health concerns, what matters is “ionizing radiation.” Microwaves are too low energy to be ionizing, so they don’t match what most people think of when they say radiation with the implication of ionizing.

Radiation, in this context, is light. Everything from old school AM radio, to microwaves, to infrared, to visible light, to UV, and finally gamma rays are all just photons. For light, there are two energy metrics: how much energy the individual photons have, and how many photons are being emitted per unit of time. Only the energy level of the individual photons determine if the radiation is ionizing, as in, powerful enough to rip electrons off what it hits, including important molecules like DNA. Ionizing radiation starts at the UV range, so anything below that is not ionizing. This is why you can get skin cancer from UV but no amount of visible light can cause cancer. And microwaves are well below even visible light so they aren’t ionizing either.

Also, Wi-Fi and cellular networks operate in the microwave range. In fact, your microwave oven is 2.4 GHz, which is what older Wi-Fi equipment exclusively used, which is why your Wi-Fi connection used to crap out when you microwaved something. The reason you don’t feel your hand heating up from the microwave rariation coming out of your phone is because the number of microwave photons per second being emitted by your phone is far less than a microwave oven. Your phone’s antennas are 1 or 2 watts while your microwave is over 1000 watts.