> Modern Russian has 6 cases (with a couple more that pop up very rarely) with 3 genders and singular/plural endings. It's a total of 36 possible combinations, which is not that bad.

36 isn't that bad but Russian also has 253 irregular verbs [0], each of which adds another set of combinations. A lot of them are just small tweaks and there are some that follow a set of patterns (e.g. идти with its various prefixes) but it still adds a lot of overhead.

[0]: https://en.wiktionary.org/wiki/Category:Russian_irregular_ve...