Unions are just a framework. If you dig a bit you’ll find there are factions in almost every union fighting for more democracy and benefits for the members, and many of them are winning. Two off the cuff examples are Teamsters for a Democratic Union and CORE from the Chicago Teachers Union.
EDIT: it would also be remiss not to add that much of the power of unions has been stripped away by union busting and bad legislation
Worker democracy is the characteristic that's most useful. Regarding that, imo there's a good case to be made even to the conservative side of the aisle in favour of unions, as at its best they can drastically reduce the need for strong top-down regulatory legislation in favour of much more specific, granular agreements between workers and employers made from the bottom up. But the power to be able to do that has been crippled (for good reason in some cases! But not all).
EDIT: it would also be remiss not to add that much of the power of unions has been stripped away by union busting and bad legislation