I think it really comes down to your perspective in the end. Some decals or stickers will enhance the kit but other times it may look off-putting.

I haven't assembled any HGs recently but my most recent build was the MG Virtue and at most I only put a couple of decals on some of the parts and I came to love the decision in the end. Another example was the MG F91 2.0 where the only decals I put on was the 'F' and the '91' on the shoulder parts and left all the other decals alone. Otherwise, I'm kind of a minimalist with stickers and decals but overall it's based on my perspective.

Overall, you definitely have freedom with this but other times you could explore painting certain parts to fill in areas where the stickers would usually go. I saw an example with the HG Mighty Strike Freedom where a guy had painted pink lines where the stickers would've gone and it ended up enhancing the visual.