So in theory, if you had a planted tank with no fish and were EI dosing you could get away with never doing a water change as long as your lighting and CO2 were in balance?
Well, till you started hitting upper bounds of salt stress with the plants, which might take a long time..........
Plants=> Fish => Shrimp is the flow for increasing sensitivity to nutrients.
Plants are very tough.
I'd still suggest a WC every 3-6 months.
Or you could test if you have some adverse reaction and break in hives anytime anyone suggest a Water change. Likewise, you could do a water change if you know you will not do any test kits.
Water change is par for this Hobby regardless, test kits can be optional, but useful if used correctly and consistently, which tends to be rare IME with hobbyists and clients.
The NON CO2 is non CO2 with good reason, slow things down like LABOR, which is a good reason to have slower plant growth in a non CO2 tank to begin, you want to avoid BOTH test kits and Water changes, eg.....labor.....but still have it look good.
I get all sorts of bone headed arguments trying parlay the CO2 and pull off no water changes/no testing etc...........if that is the goal, non CO2 is the simply put: the BEST method available.
I really do not understand the ignorance folks often have towards non CO2, it's right in front of them, but they avoid it(not you, but folks in general).
It is without any doubt,
the most sustainable method there is. And it can look quite nice for the lazier among us or the time strapped. CO2 is the single largest killer of fish and cause of algae, and too much light a close second for algae.