Is "forced" really the right word, though? We're talking a typical difference of 20-40 potency per charge... versus at least a global's worth of uptime, if not however long is required to get a Raise and then 25% of your potency for 90s thereafter.
If the dedicated knockback-prevention button weren't there, it'd more than fair game to ask that the players advantaged by having a gap-closer think some 30 seconds in advance to utilize that otherwise free advantage.
Note the bold, though. They certainly weren't useless until they were deliberately devalued to next to nothing.
Here, too, consider: Neither the current reward nor the current accommodation have anything to do with the fundamental design of positionals.
Take this shocking notion, for instance. What if... bear with me here.. we didn't have bosses leap to where their entire rear sectors are inaccessible, instead being even just a quarter of their hitbox deeper into the arena, for instance? Or, in the cases where, thematically, they need to leave the platform entirely and thus cannot be accessed by rear or flank, that they become positional-less over that period only. Huge, fundamental change, I know, but it's just a hypothetical.
I mention this only because we often seem more eager than we should to conflate a poorly managed (or, less euphemistically, sabotaged) situation with a poor design. If it a gameplay loop we are discussing, then we ought to be looking it as a gameplay loop, determine whether it's worth having or not, and either reward and situate it appropriately, or remove. We should not remove it just because it is not presently sufficiently rewarding or situated.
In the end, though, I think the idea of positionals is honestly going to come down to one thing: Do the people who actually enjoy melee DPS, for their gameplay, enjoy the added business of positionals? If not, we should see if there are any parts within the broader mechanic that are responsible for the dislike, and if there are any parts that would be missed.
But, imo, the last thing we need is even more gameplay being gutted in the name of accessibility towards those who had little to no prior interest in the affected role (e.g., "would-be" tanks who don't actually enjoy managing enemy positioning, appropriately timing mitigation, or healer-interplay, etc., anyways). The actual invested/interested party should be at the center of any decision to remove (or keep, for that matter) a given mechanic or its related area of gameplay.
Again, that it has been murdered has no bearing on its fundamental design. The same question stands: Do we want it (A) not dead (revitalized, polished, and meaningful), or (B) gone?