Totally agree. One of my bands is a cover band within a specific genre: 80s. (So there.) But even within that, we try to keep to a theme (mostly danceable new wave) and only veer from that narrow band when we need a change of pace or for a specific purpose. Seems to work really well because venues and patrons know what they will get and can dance the night away the whole time. We don't stress out about matching "tone" or even instruments (heck, we do it all with 3 guitars, bass and drums - that's right, no keys or synths).