You’re confusing 2 different topics.
1 is “are people allowed to play however they want?” That’s your point.
2 is “Classes are ‘supposed’ to be played however players want to play them.” which is the point of the poster above.
He implies that classes are not designed with any supposed playstyle in mind. This is what is objectively wrong. All specs are designed with a specific way to be played in mind, no exception. Now if you want to go offroad and do something else, you’re completely allowed to do that. You will notice your performances will be drastically weaker, but if this is what you want to do with your sub, like you said, no one can stop you.
The game is already telling people how to play for the most part, when the tooltip says skill X does more dmg after skill Y, they’re not telling you to spam skill Z, they’re telling you to do Y first and then X.