"Throwing together" anything using anything is not really that hard, but understanding the problem, making trade-offs with limited time and budget, writing maintainable and well-tested code, making something easy to use, accessible, efficient... these are all very difficult to pull off regardless of whether you're building a CRUD site or not.
I would also disagree that the web dev learning curve is not that steep... sure to get something to "compile" (well, show up on the screen) is stupid easy (<p>Hello world</p>)... but to actually make a functional, usable, performant, efficient, accessible, beautiful site or app requires managing a lot of complexity across a bewildering amount of environments and tools.
I'm not saying all web software is simple and all web devs suck. The fact is that most web apps are CRUD, and not well designed or 'beautiful' and written by devs that really don't care about SWE or broadening their skill set - just collecting a pay check - and that's fine. The ecosystem of operating system, compilers, distributed systems, embedded etc is a bit more rigorous because the bar to entry is higher.
I would also disagree that the web dev learning curve is not that steep... sure to get something to "compile" (well, show up on the screen) is stupid easy (<p>Hello world</p>)... but to actually make a functional, usable, performant, efficient, accessible, beautiful site or app requires managing a lot of complexity across a bewildering amount of environments and tools.