From what I understand there are a fair number of stairs for some rooms (e.g., the villa) at Casa Palopo, but some rooms are more acessability-friendly, so I would just ask about that. I was somewhat surprised by the lack of alternative 5-star properties around Lake Atitlan, but there were a few nice looking airBNBs - Casa Prana and Laguna Lodge looked to be the most competitive alternatives but appeared a step down.

Also flagging just because you mentioned visiting in 2023, a group of us were scheduled to visit Guatemala last week, but there have been political protests that have blocked most of the highways and routes outside Guatemala City that forced us to cancel. These protests have been ongoing for ~2-3 weeks now and have recently started to turn violent (riot police, shootings). Casa Palopo cancelled our reservation for free, but from what they told us the blockade would make transport from Guatemala City to Atitlan possible only between 11 pm - 6 am and would take 2-3x longer than usual (8-12 hour journey). Hopefully things get better soon, but just wanted to note in case you weren't aware.