And yet nobody said "avoid ultra-processed food as defined by NOVA". They said "avoid processed foods" and "eat whole foods". It's extremely generous to assume everyone reading the former translates that in their head to "avoid ultra-processed food as defined by NOVA". And the latter is meaningless.
Even if that is what they really mean, that's really surface-level advice. There are foods in Tier 4 that are just fine. There are foods in Tier 4 that are more nutritious than "whole foods" are. Note that if you add whey protein to your soy milk, you have just created an ultra-processed food!
Simple-and-implementable is something you can deploy in the moment without knowing things beforehand. If you're at a grocery store, you can ask yourself "is this really processed?" as a simple filter that will largely steer you right. Similarly, Michael Pollan's advice to "Eat food. Not too much. Mostly plants" resonates with a huge number of people because it's a simple, actionable, not very fussy way to approach eating.
Complex-but-accurate advice is stuff like 'let me look up if this follows the definition of tier 3 or 4 processed', or 'I have to have 5g net carbs today and this is 1.2g so I have 3.8g left'. This has a much higher cognitive load, requires a lot of research and pre-planning, and is unlikely to be implemented in the moment nor sustained long term. It's also a place where people can develop unhealthy psychological relationships with food and eating by being hypervigilant about complex rules.
Most people find their lives work best with simple-and-implementable rules of thumb for food.
Looking at the entirety of your comment, you should really apply this advice to yourself.
Highly processed or ultra-processed food is absolutely a meaningful term. The United Nations published so-called NOVA food classification which divides food into four categories by the amount of processing it received.
Category 4 is what OP was talking about. Industrially processed stuff full of preservatives, artificial coloring, hydrogenated oils, protein isolate, maltodextrin, invert sugar etc. Unlike the other three categories, this sort of industrial processing is a relative newcomer, it wasn't even a thing 100 or 150 years ago, so it is entirely plausible that our guts and our gut biome may not be happy about it.