Yours wouldn't be the first occasion upgrading to newer faster tech revealed problems in equipment.
Lumos fiber was made available here last November and could NOT get signed up fast enough. I went with 1 gigabit (up and downstream of course). I'm an I.T. guy so I like to roll my own equipment. I had the install tech setup the new box in transparent bridge mode so I'm not using their box's wifi or as a router. I thought my Mikrotik cloud router with four 10gb ports was sturdy enough. Nope! It's gigabit ports I had my service connected to could only muster 350mbit. Directly from the Lumos box, almost 1,100 Mbit/sec was available. I don't recall having any stuttering issues, I just couldn't reach the speeds I paid for.
I too the plunge and bought further into the ubiquiti/Unifi ecosystem. I ended up getting a Dream Machine Pro Max Gateway because it has a pair of 10GB ports to allow for faster fiber connections in the future. I also snagged one of their Pro XG 10 POE 10GB switches so I am fully 10gbit throughout.
https://store.ui.com/us/en/category/cloud-gateways-large-scale/products/udm-pro-max
https://store.ui.com/us/en/category/switching-professional-max-xg/products/usw-pro-xg-10-poe
Using SFP+ ports on switches allow one to choose between both 10GBit copper or fiber connections directly to devices. I have a purpose built Audio PC in my He-Shed for listening. It's connected via fiber optics.
I seem to hoard digital audio files in FLAC, WAV and DSD formats storing about 40TB of audio alone. Currently I'm converting from Windows Server to unRAID server for my digital hoard.
I use an Asus RT-BE88U WiFi 7 router flashed with Merlin router OS and running just as an access point. I get in excess of 900mbit/sec on wifi 7 wireless connections.

