I suspect although your printer is now working with wireless, it's not really using the 5 GHz network spectrum. Most 5 GHz capable routers can set up both a 5 GHz connection and a 2.4 GHz connection for backwards compatibility with devices that aren't capable of supporting 5 GHz.
Sometimes a router can be set up with both 5GHz and 2.4 GHz connections with different names (usually by adding a "5GHz" to the end of your chosen network name) so you can choose which network type you want to connect to. Other times just the 5GHz network only is set up, using the name of your choice.
However, there is also an option that sets up both a 2.4 GHz network *and* a 5 GHz network with the *same* network name and password. Perhaps that's why your 2nd router worked and the first one didn't. The printer grabbed the 2.4 GHz network but your phone and/or other devices grabbed the 5 GHz network (for devices that had a 5 GHz capability), and everything was still able to "talk to" each other since the same network name and password was used.
The problem for me was that sometimes my 5 GHz devices would "downgrade" to the 2.4 GHz network because the signal was stronger (but much slower), or maybe for other unknown reasons (network capacity? random choice?). Using separate network names allows you to force your devices to use the "fast" 5 GHz connection by specifying the distinct 5 GHz network name. However, once I set that up, my Canon MX492 could no longer connect because it was incapable of seeing the 5 GHz name.
To solve the problem, I connected my computer and the printer to the 2.4 GHz network name, but left our phones and other 5 GHz capable devices set to use the 5 GHz network name. Normally, that would make the computer slower, but it seems that I can have the computer connected via the Ethernet cable (fast), and also have the wireless 2.4 GHz network name activated as well. I can now print and/or scan from the computer to my MX492 successfully, and happily, a download/upload speed test proved that the computer was smart enough to use the faster Ethernet connectiont for everything else but connecting to the printer.
Unfortunately, that means we'll have to manually select the 2.4 GHz network name on our phone's wireless connections when we want to be able to print directly from our smartphones - - but we don't do that very often so it shouldn't be a big problem for us. The only problem is that we would always need to remember to re-select our smartphone's 5 GHz wireless connection name after printing is done, so our phones will be fast again for other downloads and streaming, etc.
