Oh man, that restaurant site thing hit home for me. We had this bakery client that wanted their homepage to have all these particle effects and floating images, and it was a total mess on older phones. Spent like 3 days debugging frame drops before I just ripped it all out and used basic CSS fade-ins with a 200ms delay on each section. Looked cleaner and loaded faster too. Sometimes simple really does win.

Start brushing everything you used to scrub with soap and water. Had the same wake up call with a cast iron pan I was scrubbing too hard, ruined the seasoning completely. It's funny how we think more aggressive cleaning is better when sometimes gentle is the way to go, like with those fragile slip layers you mentioned. Makes you wonder what else we're being too rough on without realizing it.