MIMO improves throughput if you have an Internet link it can saturate; realistically even a midrange 2x2 802.11AC router will provide more wifi bandwidth than your internet does.

And that's where the fat controller says you are wrong. I have 1000 Mbps down. I've yet to actually hit that speed with WiFi 6.

Also newer WiFi standards significantly improve latency. That's nothing to do with having more antennas though you would be correct there.

The meme is correct. A $6 ethernet cable beats any and all wifi routers and client adapters, and always will.

With current technology you would be correct. But as for the always part: Ethernet is an electrical signal, so it's actually slower than microwave signals used by WiFi, and the WiFi signals can also take a more direct path. So in the future WiFi or LiFi could in fact be faster. It's the processing delay, and scheduling that makes WiFi have higher latency. Not the physical medium.

Before you say this is all academic because of the small distances involved I would remind you that propagation delay is actually a large issue in current microelectronics and computers. Sometimes parts of the same chip are far enough apart to create problems for the engineers due to the high clockspeeds of modern devices.