well I do admit they are not the best connection that can be done, but I have also seen plenty of poorly crimped connections from using the typical multi-purpose cutter/stripper/crimper like this:

If you are going to do a crimped connection then I highly recommend the ratcheting style like this:

I always use a little dielectric grease on the blade area to help seal the connection and the natural tension of the wire sheathing also helps keep the connection resistant to water.
I have probably every type connection either in my shop or available at my job, yet I do still use these from time to time simply for the quick
convince or the in the case where I want to remove it at a later time and with just a sample piece of shrink tube the spliced area is repaired.
My enclosed trailer was completely wired using these connectors from the factory and I have yet to have issues from them.
But there is better connections as you have mentioned and I would recommend using them as long as a quality connector and crimper is used.
But please avoid the cheap connectors and multi-tool crimper's from places like Harbor Freight other wise I would go with the blade splices I have shown along with a little dielectric grease.