I don't have an issue but I can understand the complaint because it wasn't just a throwaway line. But I wouldn't have Vegeta wait until the Cell Games are over to unlock SS, he already struggled with it for the entirety of the Namek arc, with all that build up he better be stronger than Jiren when he gets the form.
And having three SS being unable to deal with the androids raised the stakes much more than just one of them losing. Perhaps, the answer would've been to soften Vegeta a little bit due to the Bulma effect, just enough for him to be able to unlock the form. Expedite the Bulma effect just a little.
And while it does undermine the previous theme (and the legend itself), the technicality that he has a pure heart, a pure evil one is pretty funny.