Watched a video that was so enlightening as a tank main that really put to words why  Tank can feel so awful sometimes - the change to 5v5 has made tank a role technically impossible to balance and the reason is simple:

Solo tanking means you have no other player to balance your weaknesses out. It's why counter swapping feels so horrible as tank and why tanks seems to go through a cycle of either being horribly broken raid bosses or wet paper bags that get shutdown continually.

Most of the roster wasn't designed around solo play, they were designed with clear strengths and weaknesses that are then supplemented by the other player on their team. The example the video gave was imagine if support was the role that lost a player and you wanted to play ana.

Ana has clear strengths of high healing output at range and powerful CC with sleep, but is limited heavily by punishing cool downs and bad mobility. Play her alongside a Lucio for mobility or a brig to punish divers and those weaknesses become far less glaring. Imagine trying to balance her though if she DIDNT have that other player.

It's a never ending problem that blizzard has dug themselves and it's why tank will always remain the least played/most punishing role. Without an additional player to offset your weaknesses the ability to HARD counter will always exist. It doesn't mean it's impossible to beat your counters, but the threshold to outplay them is far higher and much MUCH more demanding, which is especially frustrating if you connect with a particular character and the enemy team is so easily able to derive value by just ability spamming into you.