I get what you're saying. Obviously everyone draws their lines in different places. I won't tell anyone how they decide what makes using old computers worthwhile to them. If one asks, "why not just use the new computer," then that's fine, but I can't relate to why they're trying to get their 68000 on the internet. Surely we're not trying to find solutions for real legacy users are we?
Still, I think the OpenWRT solution isn't bad as far as ease (when compared to the previously mentioned serial/ethernet Xport component from Lantronix) or power/noise (when compared to a host computer). I mean, it's just a router. It "feels" like a legit solution. You can't "just use the router" to access the internet.
And I'm ancient enough. I went for several months with nothing but a Televideo 910 dumb terminal and a modem when my IIsi died in college.