I'm wondering if you have the old firestick which is the non-4k model. That could explain the video quality.
I’ll have to look back at my Amazon purchases. I bought the larger FireTV device, not just the smaller Firestick because there was an adaptor to hardwire it.
Maybe that was the difference? This ROKU had a direct connect Ethernet connection whereas I had to get an adapter for the FireTV?
Either way at worst it’s a more current device and I have an extra FireTV device I can throw on our porch television now.