I Know Banner of Command was Removed, but...
Why aren't we talking about the fact that a Banner of Command minion took longer to kill than a tower, at any phase of the game that it was normally purchased (by the time a team is pushing Tier 2 towers)? That's not a flaw in the item, that's a flaw in tower strength.
There was a point in time where towers took so long to kill, sometimes multiple sieges. Back in Season 5 and prior, inhibitor towers were standing 40 minutes into the game with 45 seconds on the rez timer, and there wouldn't be a forfeit vote. Instead, it was thought that ending the game was possible, but not probable.
Now we're in an age where if a player sees the entire enemy team mid around their team's dead outer turret and the player still has one minion wave to clear before reaching the inhibitor turret, the player can clear that minion wave and kill the turret 25 minutes into the game before the enemy team reaches them, even if the enemy team instantaneously reacts. The player will die, but the point is killing that tower that early into the game in that duration of time wasn't even possible before Season 5.
And that's how Banner of Command minions felt. They genuinely felt like a lesser version of old towers. It would take a solid 20 to 30 seconds to kill it as your standard AD bruiser or carry, even longer for an AP champion.
By no means should towers go back to their old state where games commonly lasted 45 upwards of 70 minutes, but towers are so weak nowadays where they can be taken down quickly and it's so easy to turret dive. They're not even a safe-haven anymore like they used to be, where players would tower hug and farm if they were behind, and feel like they still have a chance to catch up doing so. Now towers are just a means to end the game, where if a player is behind they'll either get solo dived over and over by a bruiser in top lane, double dived by jungler in middle lane, or quadruple dived by mid and jungle in botlane, then the enemy will just take the tower and go take another objective.
Towers need to be buffed and feel like safe havens again. If Banner of Command were to give the same defense as a tower in the game right now, it wouldn't even be purchased, and Zz'rot would be used as an alternative if either were to be used at all. This is why it's a flaw in towers and not in the item.