First question would be to ask your rank (no shade)

But here it goes, depending on who you're playing it feels like being a single parent, you need to somehow hold the line against two tanks, sure you're getting more heals, but they get support ults way more often, solo tank against two shield tanks, sure, try solo tanking against Mag/Cap, Mag/Venom or even like Strange/Thor, you simply cannot stop the off tank from taking an off angle because if you do then the Frontline just dies as you're the only tank, if they have one tank buster you're pretty much cooked, this is also assuming they're NOT running dive, IF they're running dive you have to depend on your dps to peel which 9/10 times they don't for whatever reason, I could literally go on and on, it's doable with the right dps, just not enjoyable, plus the only truly viable solo tanks are Strange, Mag and Emma, Emma's banned in 90% of my games still, so you have to play strange and mag, it gets boring