People also have strong reactions to anything new, although half the comments on reddit are shit like "omg, we have to stay together!" "omg we have to stick with tank" which means they are shit players anyways since that exposed they were probably the "lol me solo entire team on McCree!!!" mindset. I think the mode has promise, but it needs additional tweaking to be really viable.
1) Healers probably need to be buffed a bit
2) 3rd DPS being a sniper puts some of the non-barrier tanks at a disadvantage. Winston/DVA/Hammond dives aren't as viable because it leaves the rest of your team exposed to enemy team
3) With a solo tank, they are extremely vulnerable to disables (hack, freeze, etc). Maybe buff tanks so CC lasts a lot less/has a lessened impact
Some of the tank changes are pretty nice (Rein hits like a fucking truck, Zarya AOE bubble is amazing), but some tanks (like Winston) have less of a role and would need additional tweaks/buffs.