I think that gravel/sand vacuuming is necessary is another hobby myth (like the one inch per gallon rule, or that we need 4x to 10x water flow through a filter(s), or over filtering is necessary or good! - things like this are perpetuated by well meaning hobbyists, but just aren't true).
Once organic matter decomposes, the result is a humus like material that has nutrients, but is no longer a pollutant....so what is being removed is relatively inert. And if there is a sufficient clean-up crew, it's minimal. Also, for rooted plants it provides organic fertilizer.
Now there are some exceptions. Very coarse gravel and some decor may allow too much fish food and waste to routinely get trapped down under. Also, undergravel filters can especially become "nitrate factories".
If you have a sand substrate, especially if you also have Cory's, and Malaysian Trumpet Snails you'd never need to touch the substrate.