Remember: Champion was one of the lowest satisfaction subclasses (beaten only by Berserker and Beast Master, IIRC) in the lead-up to the 5.5e playtest. Yet Champion was also, consistently, one of the most-widely played subclasses, and so was Berserker! Why is that? Well, one simple reason is that the two of them were freely available, so more characters would get made with them. Another is that people like the idea of the "simple" warrior....but they may be unhappy with the specific execution. Since there's really no other options besides Champion and Berserker, people may still do that because they value the thematic expression, even if they dislike the rules associated with that thematic expression. If someone truly only enjoys the thematics of being a warrior, and truly dislikes the thematics of being a spellcaster of any kind, the choice is either to stop playing 5.0 (which, for many, wasn't an acceptable option, I'm sure, since 5e is often the literal only game in town), or to continue playing something they really don't like the rules for very much but which has the thematics they prefer.