There's a point beyond which LLMs are an overkill, where a simple script or a "classic" program can outdo the LLM across speed, accuracy, scalability, price and more. LLMs aren't supposed to solve "universal computing". They are another tool in the toolbox, and it's all about using the right tool for the problem.
Now, most arithmetic is done by computers, spreadsheets are done by computers, and almost all assembly language is written by computers. People have moved on to higher level programming languages for communicating ideas to computers. Would it really be that surprising to learn that in the future people use natural language to speak with computers?
The company I work for went through a big AI push about a month ago. Before then, almost no code was written by AI. Now, it's the majority of code. I'm not saying that AI coders will be able to replace people, because the AI honestly is just not as capable - if it were interviewing for my company, I would not hire it. But the thing is that I can go from design doc to prototype using less than a day and $10 of tokens. Sure I have to make corrections and rewrite some of the more fiddly bits, but it saves me a ton of typing.
And LLMs are not limited to programming. Any computer-based task that you would allow an unpaid intern to complete for you would be a reasonable fit for AI.