IMO you're not "overstating Japanese [verb][0] regularity a very little bit", but severely overstating it. The ichi-dan / go-dan verbs are indeed quite regular, and though there are irregular verbs like the grandparent post's example, IIRC there aren't actually that many (three?). However, that's not the only "axis" one could conjugate Japanese verbs. The complicated stuff are the transitive / intransitive forms, and the compound verbs. While some rules apply, they are more like the "I before E, except after C" English spelling rule.

It would be akin to saying that there are only three verb tenses in English: past, present, and future; simple, right? While it's technically not wrong, it's glossing over the progressive, perfect, and subjunctive forms (maybe there are more, don't remember), and their combinations.

[0] Hopefully from context it's clear we're only talking about grammar pertaining to Japanese verbs, and not Japanese in general. Japanese grammar has plenty of quirks, like how some colors are adjectives (red: akai, blue: aoi) but others are nouns (green: midori, purple: murasaki), or how loan words are usually written in katakana, but tobacco is not, etc.