Some time ago I was playing around with 10GbE using a Macbook Pro. At the time that meant a Thunderbolt adapter (and still does). Thing is, the one I got was essentially just a giant heatsink [1]. It was a beast and belied just how much of a problem heat distribution was. I'm not an EE so I'm not really sure why, other than by looking at what high bandwidth cables have done since.
10baseT (!0Mbps) came out in 1990 (there were non-twisted pair earlier versions). "Fast Ethernet" (100Mbps) came out in 1995. Copper 1GbE came out in 1999. Copper 10GbE came out in 2006. Ethernet seemed addicted to 10x'ing every version and 10GbE is really where everything fell apart. Or at least, it's where it got hard. We never really got mass market 10GbE. The controllers were too expensive. The cable requirements were quite high. And heat was an issue.
1GbE really was fast enough and 10GbE was a massive jump that I even remember thinking at the time that there should've been intermediate steps, which is what happened in 2016 with 2.5GbE and 5GbE.
Now compare to Thunderbolt, introduced in 2011, which has completely surpassed Ethernet bandwidth, in part by putting chips in the cables, but of course the big difference is cable length. A copper cat 6/7 cable can get to ~100 meters, which is also why the power is so high: attenuation.
but I guess my point is that 10GbE over copper was a mistake. We'd reached the point where you really had to swap over to fiber.
I don't think that's quite true. Unifi 10GbE switches are cheap enough I have a 24 port PoE+++ one in my house and my 3 main WiFi APs are 10GbE connected. My MBP uses a 5Gbps Thunderbolt adapter that runs relatively cool as well. All of this is over the existing Cat5e wiring.
I'd say 10GbE has arrived. It is relatively cheap, most of the time works over existing 1GbE cabling, and gracefully degrades to 5/2.5/1Gb based on conditions when it can't reach 10Gb.
Yes to be 100% guaranteed of getting 10Gb even in bundles of 100 cables running over noisy fluorescent ballasts to a full 100m you need Cat6A but in many environments Cat5e or Cat6 is more than sufficient. It works so well if you fail to get the full 10Gb I humbly suggest you re-do the terminations on both ends before considering replacing the cable.