Claim: the routing and security features on the edge devices your ISP provides as CPE are not sufficient
Claim: You want the ability to reset the shitty CPE your ISP gives you without losing LAN connectivity
Claim: Specific purpose devices are often better suited to their tasks than all-in-one devices
Solution: Treat your ISP-supplied CPE as a dumb device. Put a smarter device behind it that does routing, segmentation, translation, dhcp, etc, the way you want those things done.
Ideally, do PPPoE or something from the smarter device across the CPE, because CPE firmware is so often just terrible, but if not, double-NAT is often fine.
Critically, make your wifi APs a separate function both from your core home router and your edge device.
For a trivial amount of money, you can keep buying Ubiquiti APs and place them all over your property, as needed, and get an arbitrarily high level of speed and coverage. The configuration is completely painless, and this setup is completely independent of your edge device and edge connectivity.