We using MongoDB for many internal projects (ASP.NET Core) in our big company. Biggest replica-set - 3x(8 Xeon cores and 32GB RAM) has 600 inserts/600 update/500 deletes in second without any sharding.

Average document size ~ 50 - 300KB. It work perfect with authomathic failover, when Oracle with their CLOB types collapsed with Disk IO. MongoDB save a lot of time for us.

But first you need to understand how it works and then you'll love it too.