I think with a different approach to review UX could make opportunities to mix up the reviews in a way that doesn't feel like you have an impossible backlog to go through.
To be honest, I'm not familiar with Anki but I'd have to assume that there's a setting where you can change the number of review items.
You can change the number of review items but it doesn't change the fact that you have an impossible backlog to get through. Then people just get bored and churn.
Anyway, for me personally, things really opened up once I stopped thinking I needed to complete all reviews. Sure, I'll get through my backlog once in a while, but what I previously forced myself to do ~every day, now I only complete about once a month ~ quarter. If the backlog gets so large that it feels daunting, I'll go in and suspend swaths of cards that I no longer find compelling. But 'daunting' is relative -- my average backlog these days is around 1000-2000 cards, and that's OK.
I've been doing Anki for a decade and this model feels far more sustainable over the long term.
Timebox instead.
Let's say you can afford an hour (for example) of time per day for Anki. Start the hour reviewing what you can before entering new cards. If you don't finish your reviews by the end of the hour, that's okay. They'll be waiting for you tomorrow.
Some days will be spent only reviewing, some days will have very little reviewing and you can spend more time creating new cards for new things you've learned.
It's natural autoregulation. By focusing on just being as consistent as you can, you can make progress without the anxiety.