The vaccines have taken a hit from Delta because it slightly increased the chances of a vaccinated person becoming actively infected (not a huge deal), but the viral load from a vaccinated person who is actively infected is equivalent to that of an unvaccinated person (big deal). So where we could assume someone vaccinated wasn't very likely to spread Alpha if they did become infected, the same does not hold true for Delta.
The vaccines are still extraordinarily good at keeping us from becoming severely ill, hospitalized or from dying.
I actually asked this question the other day - could we accidentally "teach" the virus to evade the vaccines...I believe it was either
@hopemax or
@Heppenheimer who answered "not really" because the vaccines specifically inhibit the virus' ability to reproduce within our bodies. If the virus can't reproduce, it doesn't have a chance to mutate (I think I've got this right). Perhaps one of them can answer whether Delta has changed the answer to this question since it infects vaccinated people and spreads from them more easily?
ETA: Also, one of the big issues with COVID is that it is very spreadable BEFORE a person becomes symptomatic.