Can Cat5e even do 2.5gbe speeds?
Oh yes, yes it can. That's probably the reason 'd etre that NBase-T exists, that you can continue to utilize Cat5e cable, to run 2.5Gbit/sec or 5Gbit//sec (less popular at this moment) over existing cable.
And thankfully, just last month or so, both TrendNet and TP-Link released some metal-casing fanless 8-port and 5-port 2.5GbE-T unmanaged switches for under $200. (I bought the TrendNet ones last week, because they were cheaper than the TP-Link ones. I paid $170 for the 8-port, and $130 for the 5-port, on Amazon.)
I think that for "mass adoption", we'll need to see switch prices drop to half that, but with COVID and shortages, I don't know how long that will take. Perhaps more people will notice that their shiny new mobo came with 2.5GbE, and upgrade because of that.
As well, as I mentioned, Comcast is now offering service that exceeds the capability of a standard 1GbE port and router.
I've been scouring the interwebs for routers that have BOTH faster than 1GbE WAN
AND LAN ports on them. There are very few right now.
Edit: One thing that confounds me. Asus makes a 2.5GbE-T USB3.0 dongle, that was originally designed for their NAS units to upgrade them, and also to work with Windows PCs (and Mac?). Why can't Asus just add the RealTek Linux driver into their firmware, such that you could plug that dongle into their routers, and instantly get a 2.5GbE WAN or LAN port, additionally, for that router? It would make things so much easier for existing router customers. (*) They probably don't want to do that, though, because they would prefer to sell you a whole new shiny all-singing all-dancing Wifi 6 (or 6E, as their newest ROG router is) router with 2.5GbE or 10GbE capabilities.
(*) I'm waiting for 3rd-party firmware to do that for the AC68U-family routers. That would make those routers EVEN MORE popular. Those are basically the modern-day equivalent of the WRT54GL routers, given how many 3rd-party firmwares are available for those routers.
QNAP does have a "QHORA-310W" or something like that,. that has a 10GbE WAN as well as a 10GbE LAN port, and SD-WAN (think, easy VPN) stuff that can be cloud-controlled (think work-from-home, corporate-controlled VPN'ing). Looks really promising (it's Wifi 6 too), but like most things QNAP, it's really obscure, and doesn't seem to get popular.