I love Grunt, I understand the complaints but it's a great system that's easy to understand and work with. It's not unlike Makefiles but the learning curve is lower with Grunt.

The Grunt team compares the complaints with the actual amount of users and realizes it's a small (but vocal) minority, and that besides those, tens of thousands of projects use and depend on Grunt existing and staying maintained.

My previous project used Grunt because at the time it was the only tool existing (besides maybe using NPM directly, but using that for web projects wasn't hip yet at the time). We looked at Gulp for a while, realized that yes it would be a more compact configuration and such, but at the same time that it'd cost two weeks to convert the project to gulp without much advantages - builds were a few times a week, so no reason to move to Gulp to speed that up by a few seconds.