You re going to switch to which, proton? I just started switching back from proton drive to iCloud. Also switching back to Password from proton pass. They were both just such a hassle, it wasn’t at all worth it for me.
iCloud has come some ways but there is still a huge feature disparity between it and competitors like Google.
iCloud is a good accessory if you're already somewhat involved in Apple's ecosystem but you have to pay if you want more than a fraction of a thimbleful of storage and it lacks many basic features and compatibilities. iCloud Drive in particular is extremely barebones and completely overshadowed by Google, Proton, and Microsoft.
Also another thing is that cloud suites need to be platform agnostic and iCloud is very ass when used from the web. This will continue to be a major thing holding it back until Apple accepts that iCloud won't truly succeed until they stop giving an inferior experience to non-Apple devices.
For productivity, the iCloud suite is getting up there. It still has a way to go to be as good as OneDrive and Google Drive imo. One important to me feature I like about Drive and OneDrive is that they don’t require you to download entire media files to be able to play them. I basically keep all my media on Google Drive for this reason. Excel and Sheets both have more powerful data formulas compared to numbers (or at least they have much better documentation on how to use them) so I prefer sheets over numbers.
iCloud is definitely getting there and if I didn’t have the niche specific needs I’d probably just stick with the 2TB family iCloud plan.
iCloud Photos for some reason still only allows you to upload JPEG files from the web. Can't even upload HEIC which makes absolutely no sense considering it's now their main photo format.
Remember that Apple had to dumb down the macOS version of Pages, Keynote and Numbers at some point (from iWork 09 to single apps) to later on release something even more dumbed down for iOS... and now we have the ultra-dumbed down version for the web.