Yes, programmers survived for decades without these tools,but back in those days, software wasn't anywhere nearly as big, and real-world expectations on software were not as high (mostly because most of the real world didn't even know what computers could do yet).
As you say, the cause for such changes is usually the result of a lack of planning. But in my experience, the real world rarely has a clear picture of what they actually want when a project starts... and if we all just waited until we had a guarantee that functional requirements weren't going to change, a lot of software just wouldn't get written at all. In my experience, when you start writing, you just develop what you can as extensibly as you know how, with the expectation that you will have to refactor everything later, and at some point, through ongoing functional requirement changes, the software ultimately begins to asymptotically approach what the client says that they want, and you get paid for your work.
You said it yourself... "in messed up cases that might be true".
A great deal of the world of software development is made up messed up cases, incomplete and constantly changing functional requirement specifications, and just trying to freaking get the job done before your employer decides to replace you with somebody else who might even be less competent than you, but will tow the company line and work for less money than you will. In my experience, the real world demands results that are not humanly achievable *without* sophisticated software development tools, and that includes using an IDE, helping the programmer to get the job done on time and within budget.
I am entirely able to develop software without an IDE... but I've never once found it very productive to do so for anything larger than toy programs.
No... it's not.... but I really get tired of seeing people here suggest that programmers who might actually require an IDE to get their jobs done in a timely fashion are somehow less competent as programmers than people who've probably never had to work on large scale projects with schedules that aren't humanly possible to achieve if you were to just use manual tools and a plain text editor.
Whether this is not the programmer's fault is irrelevant... this is how the real world of software development actually is... and a programmer who doesn't get the job done in the time that he's expected to do so is soon going to find himself unemployed. Call me picky... but I would rather be able to afford to keep a roof over my head and eat than brag about being such an awesome programmer that I don't need modern software development environments like an IDE to get a job done.
My point about correctness was more along the lines of being writing code that didn't ever need to be changed after it was first written.
As for refactoring, try using just those tools to rename an identifier that is not, by itself, globally unique, but could nonetheless be uniquely identified by software that can understand the syntax of the language, and can realize the context of every single statement and identifier automatically.
Sure, you *CAN* do this by hand... but using a tool to accomplish it over a project that may be hundreds of thousands or even millions of lines of code, spanning several hundred or thousand source files, is going to be orders of magnitude faster and more reliable.
Of course, if program requirements never changed after the initial implementation was written, this probably wouldn't be an issue.
ID is a supernatural explanation
So, suggesting that "aliens who predated us did it" is a supernatural explanation? I'll agree it's probably isomorphic to one for most practical purposes given what we know today, but is it actually one?
I see them as almost identical
Panspermia leaves the question open of where the life that supposedly seeded other worlds originated.
ID leaves open the question of where the intelligence that supposedly designed things came from.