I understand the sentiment but why change YOUR life because of those idiots? Make them change theirs. Complain to United that your seat was dirty and the cabin was filthy. Tell them to put their cleanplus team on that instead of mask instructions. Do something like that each time you fly. Bathrooms were dirty, windows were smudged, seat was uncomfortable, attendant was rude, etc. With each complaint tell them to put their cleanplus team on it, not mask instructions.