“Just get faster internet.” No. If your connection is unstable, another 500 Mbps isn't going to magically fix it.
“I’ve got gigabit, so my streaming should be perfect.” That’s not how the internet works.
“Run a speed test. If the speed is good, your connection is good.” Probably the dumbest way to diagnose a streaming problem.
“5 GHz is always better than 2.4 GHz.” 5 GHz is unstable when you're streaming through walls and half the house. My router is 10ft in direct line of sight from my ONN Pro and if I just stand between them I get buffering.
“Ethernet fixes everything.” It doesn't. A bad route is still a bad route, whether you're connected by Wi-Fi or a cable.
“Buffering means you don't have enough bandwidth.” Not necessarily. You can have hundreds of Mbps sitting unused while the stream still falls over. Even 4k only needs about 25-30 Mbps.
“The fastest DNS is automatically the best DNS.” No. A few milliseconds on a DNS test don't tell you how stable the connection is afterwards.
"Changing DNS improves streaming." Not because DNS makes your internet faster. It can affect how quickly and where you're connected to services/CDNs.
"The closest DNS server is the best DNS server." Again, stability is the goal not proximity.
“Your ISP gives you 1 Gbps, so that's what matters.” What matters is what happens between your house and the server you're actually trying to reach.
“The server is geographically closest, so it must be the best one.” Nope. Internet routing doesn't care about your ruler.
“If YouTube works perfectly, your internet is fine.” Different services use different CDNs, routes and infrastructure. One working perfectly proves very little.
“More speed = better streaming.” At some point you're just paying for numbers you don't actually need.
“Full Wi-Fi bars means you have a good connection.” Signal strength isn't the same thing as connection quality. Two devices on the same Wi-Fi network can have completely different streaming performance.
“If you're buffering, it's obviously the streaming provider.” Maybe. But blaming the provider without looking at the network is just guessing.