Most, but not all. Agglutinative languages don't seem to use irregular verbs much. When I studied Turkish, I recall learning only one irregular verb. From so

Most, but not all. Agglutinative languages don't seem to use irregular verbs much. When I studied Turkish, I recall learning only one irregular verb. From some googling, Mongolian also has very few. Japanese has a lot, relatively, at around 10 (depending who you ask and how you count). I'm not sure why irregularity would emerge from lossy transmission. I would think regularity would be a greater benefit here. I assume it's just a historical accident that arises when verbs stand on their own and you don't have to do anything with them. When you're just starting to have language, it must take some real insight to realize that there is a special relationship between "go" and "went", and it's the same as the relationship between "be" and "was". But if you regularly (ha) need to agglutinate a pile of endings on your verbs, then using unique words for each tense would quickly become a pain in the butt. I find agglutinative languages are simpler than other types of languages in many ways, and I haven't studied linguistics enough to know if that's inherent to all of them or just coincidence from the small number of such languages I've studied. Turkish plurals are perfectly regular (there are 2 possible endings, depending on the word's final vowel), and Japanese doesn't really have plurals at all. Neither language has gendered words, or definite articles. Turkish has no diphthongs, and Japanese doesn't really (depending on your POV), either. Esperanto actually looks somewhat complex to me! It reminds me of my own (failed) attempt to learn French. It seems to have a lot of baggage from the Romance languages, presumably to make it seem more familiar to those speakers. I'm a little surprised it wasn't simplified further.