Either fully commit to making the trinity actually matter -- and by this I mean putting more responsibility on those roles, e.g., healers need to have more use for their healing toolkit just as certain tanks need to much less sustain. What tanks can do is borderline ridiculous.

They either need to do that or they just need to scrap the idea of a trinity all together, have tanks remain as tanks, or just outright blur the divide and give players stronger toolkits to allow them to execute any role regardless of which class they are on.