Yeah, I have fallen behind on most anime. A lot of the anime with multiple seasons are so far left behind for me the only way I can even begin to comprehend them anymore (for the most part) is to rewatch everything, which further limits my time.
This franchise was one of the more complex because of how events overlap mid season and by the time you see it in the other series you forgot where the event took place in the first.
There are also changes in how some events play out in each series.

At least this one isn't nearly as complex as the Fate Franchise lol😂