Tanks and healers have always contributed to DPS because there has to be a differentiator to allow a floor, there has to be give so that it’s possible for more than only the most pixel perfect players to engage with the roles, but if there is give then some will exceed the baseline and have overflow ability. Those players need a way to meaningfully push the encounter forward
This isn’t encroaching on the DPS (like say WAR does to healers in dungeons) this is just a core facet of how games work.
You can argue 14 always ruins the trinity because of how much damage the supports do (a facet that’s valid but also intertwined with the lore of the character being the canonical strongest human on the planet) but the supports doing damage is at its core not antithetical to the trinity being “pure”