I have issues keeping up with large language decks, too. In my case the problem usually lies not with Anki but all the other stuff going on in my life — stressors, work, etc. There’s just a cap on what I can be juggling at any point in time and if things aren’t flowing smoothly it’s going to be more difficult to stick to working through a long deck. If I could just hit pause on everything else there would be no problems.

Retention is high so that helps keep progress between periods of deck usage at least.