Gadgets

Network congestion is indeed a likely cause. Many blame 5G but it uses the exact same frequencies as 4G, and also some more, notably for short range communication, say up to a few hundred feet.

So most of the time 4G and 5G don't make a difference, you'll notice the same improvements or worsening which can have a myriad of reasons.

There seems to be an utter lack of enough investment in more bandwidth and throughput in the backbone infrastructure.

Slapping a 5G sticker on a product is not much more than marketing in many use cases. 5G shines in highly urbanised areas, IF they build out better infrastructure that is.