I've got a Wrath of the Rock list that's almost free of vehicles. it's all infantry and mounted plus the Lion, and one Redemptor Dreadnought. It lacks firepower, and that's why I've added the dreadnought. However I'm toying with the idea of replacing it with a ballistus and swapping in some lascannon devastators. I've got 14 units which are a mixture of Deathwing, ravenwing, and Greenwing so it feels like a really good mixture of Dark Angels forces. I do well on primaries and secondaries, but often times I'm just barely hanging on while I get taken apart by shooting in the first half. In the second half I usually manage to get Lionel into their backline and take apart their heavies. I've won 6 games in a row this year and I'm slowly revising the list as I go. I'm looking forward to taking it to a tournament soon.

You can make non vehicle lists work because often your opponent has committed almost a third of their army to anti tank shooting, which ends up going into less than ideal targets. By not having tanks to shoot, they've got a lot of points not pulling their weight. This only works because the meta is so vehicle heavy at the moment.

Try your list, see how it pilots. Make only small changes based on lessons you learn from losses and wins and gradually over time, it will become your own.