"Stealth" has such a limited life span of utility. Even in the 90s Serbian air defence managed to acquire and shoot down "stealth" aircraft. It required humint but that's part of a real theatre of war.
The fact of the matter is, stealth technology means that an aircraft needs to be significantly closer to a radar for it to be detected compared to a normal aircraft. That also means it has to be closer still for a threat radar to develop a weapons quality track. Theres not really any known radar technology that can mitigate this, it’s basic physics. It’s much easier to see an object on radar that returns orders of magnitude more energy to the radar.
Stealth does not a limited utility. In fact it’s rapidly going to become an absolute bare minimum for any tactical aircraft.
Even if, for arguments sake, the aircraft is at the moment leaps and bounds ahead of the nearest peer competitor military there is going to be limit to how effective a new coat of paint will be for the B-21 in 10 years time.
To get your monies worth from this thing you'd want a lot greater effective service life than that and without stealth the B-21 would have dramatically diminished it's dollar to effectiveness ratio.