You can do some research and find stronger routers for Wi-Fi from Asus, Ubiquiti, etc.

You can also expand coverage with WAPs e.g. Wireless Access Points. Lots of brands to choose, but Ubiquiti is common. Run cat6 cable in attic or crawlspace from router to somewhere central and install WAP in ceiling. 2000 sq. ft sounds like at least 2 WAPs one at each end or one on each floor.

You can look into mesh networking devices but they increase latency and can be unreliable.

4K streams are heavily compressed. It generally ranges from 5Mbs to 25Mbs depending on factors. This is why physical media is championed so much. A full bit rate 1080p blu ray will almost always have more detail than a 4K web stream.

But most people are not paying for 4K premium content. And compression tech like AV1 will help lower the bit rate when adoption rates are better. Look up AV1 vs VP9 vs HEVC vs AVC. It’s looking to be a major improvement.

Also, these large companies are not at all structured like a home network with a single egress. They are very large networks with multiple ingress/egress, multiple cache points in multiple regions, etc. to distribute the load.