1 - When your resume includes training some of the best Tier 1 military units in the world, feel free to tell Todd Hodnett what he does and does not know. The level of disrespect that some people have on the internet is ludicrous! Not to mention everyone who has a legitimate resume, shooters like Tubb, Litz, etc., all address the significance of CANT:
https://www.accurateshooter.com/optics/canting-effect-on-point-of-impact/
2 - Every "precision rifle shooter" is NOT shooting some type of PRS match where everything is about being on the clock and shooting on a square range. There are plenty of precision long range shooters who are shooting well beyond PRS distances in terrain that is far from being square or level. In those applications, CANT is going to much more difficult to detect and can impact the chances of making a consistent 1st round hit.
3 - CANT will impact your ability to hit a target at longer ranges. That is NOT an opinion, it is a scientific FACT! A 1° CANT can produce 5 inches of lateral displacement at 1000 yards with many common cartridges. Is your eyeball calibrated to detect a 1 degree angle? Can you afford a 5" miss (or more) at 1,000 yards? How you recognize that CANT exists, and how you correct for it is up to your equipment and skillset.
4 - CANT goes well beyond how the rifle is positioned when the shot is taken. Your rifle maybe perfectly level, but is the optic mounted perfectly level? More importantly is the reticle in the scope positioned and tracking perfectly level? It ultimately doesn't matter if the rifle is level, it matters if the tracking in the optic is level!
Having shot precision long range for over 20 years with MIL, LE, Competitive Shooters, and ELR Hunters, I have lost track of the number of times that I have seen a miss attributed to a bad wind call when it was actually due to a CANT issue. For some shooters, CANT should be the last of their worries, for other shooters having 1 degree of CANT will make the difference between hitting or missing the target.