That’s not always a possibility. See for example:
https://www.theverge.com/2020/5/20/21262302/ap-test-fail-iph...
Those people didn’t need or want Photoshop or a complicated program with tons of options to convert image formats form anything to anything. Even a simpler app like Preview implies knowing where to look for the conversion part and which format to pick. They could have done instead with a simple window which said “Drop File Here”, and if it’s an HEIC, convert to JPEG. Could even have an option to delete the original, but that’s bout it.
There’s an Alfred workflow which is basically that. It does have some configuration, but the defaults are sensible and doesn’t let you screw up the important part of “detect this format which is causing me trouble and produce a format which will work”
But then you have to remember the names of 200 distinct software that all do this one thing, so you make a meta-software to manage and organize them, and you're back to square one only with more indirection
The solution in such cases can't reasonably be "everybody around the world learns to download one particular tool to fix things". In your example, the two reasonable solutions are either apple figures out how not to send image files to people that they can't understand, or the college board figures out how to convert heic into jpeg themselves. Otherwise, as in that case, most people will simply be left in a lurch.
Google could do this years ago.
It might be a problem that you have to search for the solution to every time you have it, but you'll find the solution quickly because many other people also experience the problem.