TP-Link (and I think even ubiquiti?) allow the WAPs to be used in both standalone and mesh mode. The pricing required for meshing means a standalone WAP is dirt cheap.

And the standalone plays well with any router.

Even entertaining the idea of buying an all in one "router" at this point is comparable to buying a prebuilt PC. If all you need is something that works, they can be a good choice. But for anyone who would know how to interpret performance numbers you are a lot better off building it yourself (or slipping microcenter a 20). Same here. I think it is pfsense that even sell theirs preinstalled on pretty decent hardware (that you can then reformat for opnsense...).