Hi, PG - Root rot IS a progressive disease, and it's caused by any of several fungal pathogens - Phytophthora, Pythium, Rhizoctonia, Fusarium, and Armillaria genera all have species that cause infections commonly called root rot. The best way to avoid it is by making sure your planting is able to hold little to no water in the spaces between soil particles. This can be best achieved by using/making substrates from a high % of coarse material like pine or fir bark and coarse mineral products, and/or by any of several other 'tricks' which limits the amount of perched (excess) water a substrate can hold.
For example, if you have a manageable planting, water over the sink so the substrate is fully saturated and at least 25% of the water applied exits the drain hole(s). Then, hold the pot and start moving it up and down. You'll immediately notice on the reversal from downward to upward movement, the water in the pot keeps on moving downward and out the drain hole. The more sharply the reversal of direction, the more perched water you can remove. This is Newton's First Law of Motion at work, and it allows you to remove all excess water from the planting and use substrates most experienced gardeners would avoid. It can be a real game changer for those saddled with water-retentive container substrates. Correct use of ballast (not a drainage layer) can also be put in place when a planting is established and will work passively for the life of the planting by displace substrate which would otherwise be 100% saturated.
Keeping plants tightly potted is a limitation in itself, so if you're into jumping onto the other horn of a dilemma, go for it. Better would be to repot and root prune on a regular basis (eliminates limitations caused by tight roots) and use a medium you don't have to fight for control of your plants' vitality, thereby avoiding trading one limitation for another.
If you have a moment, do a quick net search using tapla soil
as your search words to get a sense of the number of people who have benefited from learning how water behaves in container substrates.