Doing anything with those big vendors is an absolute headache, and requires a lot of vendor-specific knowledge/experience, which is expensive (and their offerings are generally expensive and/or harder to estimate pricing on).

DO/Linode and others are perfectly fine serving a sizable audience of users who do not need the complexities that those larger vendors offer.

I struggled for days trying to add more disk to an existing ubuntu image on Azure in 2018. Documentation sucked - both what was there and discoverability. Their instructions just... didn't work, the UI was incredibly .... Azure wasn't my choice - client had O365 and their 'IT vendor' had 'credits' on Azure, so... I had to go with Azure... and it was a huge time sink to do some basic stuff that is literally a few clicks with DO and Linode.

Yes, I don't think I can create private VPNs in the cloud with DO - I don't need to for most projects. The level of functionality DO/Linode/etc provide is adequate for a lot of projects, and they are growing their new functionality to serve needs in a way that seems usable by people without needing to be a certified expert in BigVendorCo.