I don't think "surprise bills" is a good reason to avoid AWS. Yes, you avoid them on other providers by doing simple bare-metal Linux boxes. But doing a bare-metal Linux box with no other services is also fixed-cost at AWS. You only get into tricky to determine in advance variable costs when you string together a bunch of AWS's extra services in ways that you don't understand well or don't/can't set limits on.

On the other hand, doing single bare-metal boxes being much more complex and usually more expensive is a good reason to skip AWS for simple projects. In addition to the profusion of instance types and billing/usage options.

I also think the lack of options on limiting max billing for flexible services is pretty reasonable actually. For most of them, there's no single obvious reasonable thing to do when the money hits the limit. Storage costs money too, but I don't think much of anyone really wants to have their data get deleted when the cost hits the limit, for example.