Distribution, marketing and running it is the hard part, not building software. I consider libraries to be like roads, it's a communal good if you will. Feel free to build and run these apps yourself in the open instead of complaining. You will see how time consuming that is.
Building a road is usually very similar to building another road.
Building ffmpeg is very different from an SSL lib. They need different tradeoffs, design strategies, domain knowledge, etc. And doing them properly is really really hard. A lot of software out there sucks, in part because there is more focus on marketing than on correctness and reliability.
If roads had the same quality as software then traffic deaths would be an order of magnitude higher.
Try working on a library used in tech that your life depends on and you might re-consider your road metaphor.
I've been a core maintainer of several (machine learning) libraries. It's a communal effort of people who care enough about these things. They come together because they need it, it's basic infrastructure so to speak.
> Building a road is usually very similar to building another road.
It's a similar process, but so is building software. That's entirely besides my point though, which you seem to have missed entirely.
Case in point: I regularly use a free iOS app that is clearly the result of someone's deep passion in taking what could have been a simple wrapper and turning it into an incredibly simple but powerful interface to complete a useful task efficiently and at any scale... and that task is exactly what OP was trying to do...
But as someone who's somewhat familiar with app store optimization, I guarantee the creator did none of that that.
Their app name would need to be something obnoxious like "Frame Grabber Extractor: Pic from Video" to capture all the different searches people do for this task.
And the people focused on distribution are even paying for ads with the money they make their IAP infested "1 week trial; $4 a week" alternatives make.
What you mention is the hard part is only because the foundational blocks are free and open source (in this example). Not that marketing would become easy, it's still difficult, but not write-ffmpeg-from-scratch difficult.
