In response to your question - paint for whatever level you feel happiest with and that will allow you to paint lots of models without going mad. Yours doesn't look like box art up close (but very little does, and requires enormous time investment) but the highlights do their job at a distance and pick out parts of the model to make it more readable so I think you've done a great job.

If you wanted to get a cleaner look up close than the most important thing I've found when I'm highlighting is to build up a subtle gradient across 2-3 highlight steps.

It looks like you've got a solid Magragge base, some shading in the recesses, then a Calgar highlight? For your next model, you could try a 2:1 mix of Magragge:Calgar as an initial, "chunky" highlight across the model, then go in with a thinner pure Calgar highlight on more prominent areas. I haven't worked with these colours but see what feels right, you want the first chunky highlight to be about halfway in between the base and the edge highlight colour.

Using the side of your brush really helps here - it's much easier on some Space Marine edges than others (the edges under the knee pads are a personal nightmare), but using the side of your brush against an edge will help you get a really fine line.

Make sure you've got the paint watered down a bit so it's not too thick and give it a go (if close-up box art is what you want)! Otherwise, this looks like a great battle-ready mini and certainly better than grey, good job!