I'm aware of plenty of airlines who are not transparent with their fees and are often advertised as much cheaper than some of my preferred airlines.

I don't trust the price I'm quoted until I get to checkout, but if I don't even SEE them in my list of flights to compare, they're not likely to be a consideration.

A lot of flight aggregators also support filtering in/out airlines and I often do this with those who are sneaky about their fees.