I imagine at least some of the bad reviews are there because DO serve the absolute bottom end of the market and with that comes a specific kind of difficult customer.
They offer a lot more than just VPS services.
But compared to the likes of AWS, Azure and GCP their pricing structure is simple and predictable.
That coupled with the straightforward management interface, team management & access control systems make it a very inexpensive and approachable solution.
It just has a really low barrier of entry, and its partially why I chose them for some projects with my current employer. There isn't enough rope in the management UI to hang yourself with, and I can handover the lot to my replacement even if they're not particularly clued up on system administration.
So to answer your question, I see DO as offering a subset of what AWS/Azure/GCP do, with the cost and complexity savings to reflect that. So those larger cloud providers are what I consider the higher end.
I realise AWS is a giant outfit, but comparing and contrasting their EC2 admin panels with the DO one, you'd be hard pressed to say AWS feels like a premier solution.
The bottom of the market is the no-name companies that offer VPS for $1/month or so, or even less in some cases. Can't comment on the quality of these offerings but I have to assume most if not nearly all of them are pretty bad (and forget about support).