I have never understood why using different vendors is such a big problem for many people. Each vendor is better than others for certain aspects, but no vendor is better than others for everything. At Kokoen, we usually host the applications we develop in AWS (EC2, RDS, S3), use Firebase (usually with OneSignal.com) for notifications, use Netlify for hosting certain SPAs, use Heroku to provide APIs directly from Git while we are still developing, MongoDB Cloud when we need NonSQL databases, etc..