With AWS although you have to pay the premium on egress, you don't pay that until you leave their sandbox; what's more, you can add links into your VPC that sidestep it. If you're just running open source software or a kubes cluster on commodity boxes and you're fine owning all of your operational burden, sure. Use whatever you like. But if you want reliability and good DX, your options get narrower.
Personally, I think that AWS Code Suite and VS/Azure spaces (and GitHub spaces by proxy) are going to be the real challengers in this space. There is a real UX problem to solve but it doesn't mean I want to necessarily use a different platform.
If Render is good enough for Stripe's production workloads, then it's good enough for mine.
It's about ecosystems. Heroku has a decent ecosystem, but nowhere near AWS or Azure. I find it far more likely that AWS and/or Azure will improve their ecosystems to attain parity with the gold standard Heroku (or Render for you) DX in the small but which can scale all the way up. But you may find that a tall tale, and if so I would understand. The track record on the AWS/Azure side isn't great. But the latter did acquire GitHub, and I fully expect them to exploit that. I would be surprised if AWS lets them 1-up their incumbency through that vector without neutralizing it.
If you want something managed that requires minimal time worrying about infra, they're a great choice. For something that truly requires low costs per user, I wouldn't use them but they make a ton of sense for many projects.
And to be fair, AWS also has some serious limitations in terms of price scalability compared to a VPS like Digital Ocean or Linode: https://questinglog.com/costs-are-part-of-scalability/#just-...