It is very rare that we actually work on something truly novel, and it’s even rarer that the
majority of the task/project is novel. It’s really not that hard to identify something “reasonable” for most tasks, once you’ve broken it down. The pieces that are actually novel — you make an estimate to produce an estimate (how much work do you need to do before you get a handle over it?)
Of course, the further you go out, the more your error margins (and the less others naturally rely on your estimate, and the more likely you say something generic like coming soon in 2025)
But this notion that it’s all creativity born of the ether, as if you’re sitting around waiting for eureka to suddenly strike is complete bullshit.
There is the issue that external resources will latch onto your vague estimates like it’s the word of god, and try to hold you accountable to unreasonable degree, but that has nothing to do with your planning. Usual solution there is to figure out what feels reasonable, and then double it again for your boss — and double it again for the client (which you’ll probably lose a bit to negotiation). There’s also the issue that a single heisenbug can take stupid amounts of time to resolve… but that’s why you doubled up — you keep buffer for that kind of thing.
The vast majority of any project is just plumbing — creative or not.