On a tangential note, one of my pet peeves is the way that many people (mostly Americans?) pronounce words like "processes" as "process-eez". Words with Greek roots that end in -is or -es generally use the -eez suffix. e.g. analysis -> analyses; thesis -> theses In the case of Latin, it's -ix or -ex . e.g. index - indices, appendix - appendices. There are of course exceptions and outliers (suffix -> suffixes; octopus…
I don't think it's true that languages get simpler over time.
Latin used to have all its cases suffixes, and today's Romance languages have dropped nearly all of them.