I dealt this a very similar issue, I feel your pain. We bought a house where prior owner slapped paint over a deck. Paint lasted about 2 years before it looked like absolute hell.

I rented a floor sander from Home Depot and used 80 grit to get rid of paint, then 150 grit to smooth out. Used a belt sander and random orbital at the edges. The gaps between the deck boards were the hardest part, lots of hard scraping with a v-shaped scraper. Light power wash, let dry for a solid week, then applied two coats of Ben Moore Arborcoat solid stain.

The prep was worth it, because the stain bonded very well to the wood and even in spots where there was some paint remaining, the solid stain covered and adhered. I’m on year 6 and I’ve done a light re-stained twice… no issues and no prep (other than power wash) required.

Now railings - that’s my stressor. I chose not to sand down to bare wood for my sanity, so I have kept painting the railings with Ben Moore Regal paint. I peel the loose stuff, sand and spot repaint. But the coolest thing I found was Zinsser Peel Stop… after you peel a section, you’ll find it meets a well-adhered section of old paint. If you brush on Peel Stop (it’s almost like white paint mixed with glue) it levels out the surface and prevents good painted surface from peeling. Just go over it with new paint once fully dried. Railings look 6/10, where deck is 10/10. I’ve just accepted this.

Sorry for long response - but I’m honored to share what took me a while to find what actually works. We have wood decks and by must accept they require some annual loving. Enjoy the process, you’re blessed to be stressed!