The simplest thing is the hardest
A form, a date and a phone number all look easy and are anything but.
In every platform the same three things took the most time: a form, a date and a phone number.
Phone numbers
People write them a dozen ways: +998 90 123 45 67, 901234567, (90) 123-45-67. All correct. The program has to normalise them and then hand them back in the shape the person typed.
Dates
A date is the intersection of time zone, language and format. "01.02.2026" is the first of February in one country and the second of January in another.
None of this is interesting and nobody notices it — when it works. When it does not, the user loses trust in the whole platform.