Frankly, I find most work well enough with xterm or rxvt termcaps to prefer that over having apps just refuse to even try to work until you've changed settings.

But conversely, if distributed like that, I'd also feel that this implicitly means any failure to act like xterm is a bug they've implicitly suggested it is reasonable to report or complain about (and if the version number doesn't imply it's an early stage release, and it still doesn't work well with its defaults, I'd get cranky)

If you send feature-detection queries it doesn't matter.

The nasty part is that RXVT violates ISO 2022 structure in weird ways. It's not alone in that, but most of the other-program violations are much more easily fixed.