Instead of outright banning a card, let players suggest taxes on certain cards and then filter by players that have a similar filter on that card, or don't play that card at all.

For instance, I abhor Counterspell, but it has a place. If I'm playing any of the ultimatums for seven mana, I'm almost disappointed if it doesn't get countered. However, if someone can Counterspell any early plays, the entire game isn't worth playing. I would assign a tax/filter of five colorless to Counterspell, and hopefully match with only players that either don't use Counterspell or agree with my above assessment.

Similarly, the way my favorite decks play, Nadu isn't anywhere near broken against me, and I would gladly play against Nadu without any tax.

In the long run, more players would have more good games without early concessions, and we'd all win.