Amazon created and dominated the cloud as we know it before Microsoft even knew it existed. To this day, Microsoft's prices on Azure are about twice that of AWS, and Microsoft doesn't have a prayer in taking that market. All Microsoft has ever done is a half-assed attempt to buy their way into yet-another-market. If Amazon wasn't so laser focused on defining what the cloud means and pouring in R&D dollars, sure they could make a little more money. If Amazon wasn't pushing boundaries like same-day delivery, sure they could make a little more money. Put another way, if Ballmer wasn't so focused on making a little more money, and could be laser focused on R&D and pushing boundaries, maybe he could dominate a market like Amazon - but he left that post years ago.
Sharepoint is your best bet here.
The only alternative I can think of is checking your docs into your source control.
Computer Science is the only discipline in which we view adding a new wing to a building as being maintenance -- Jim Horning