Many other iPhone/Macbook users have been shocked I don't turn on Messages on my Mac due to a bad experience with sync in the first year that was possible, and I had a similar bad experience with photos in iCloud early on. Maybe the sync is fast now, but my usage would put my in a higher iCloud tier than I'd like, and I still feel more at ease juggling many Photos libraries on external hard drives. I avoid Google Photos like the plague, and even though I trust Apple more (for now), I'd still rather not entrust to them my family's personal photos and videos.
Hopefully in a place where I can solve the bigger problems I have then!
You can use Messages on the Mac without storing messages in iCloud. iPhone, iPad and Mac can all send and receive the same account’s messages, effectively staying in sync without actually syncing them to iCloud’s servers.