just nitpicking, but technically ISO 8601 does not (currently) permit the omission of the year.
if information is to be omitted, it must be done in ascending order of significance, so you can omit, in order, seconds, minutes, hours, and days.
(if you omit the month, that’s just the year left so why bother with ISO 8601 lmao)
the “best” format for everyday use is each individual person’s personal preference.
you may be more used to DDMMYYYY due to culture, language, upbringing, and usage. in the same vein, i am more used to YYYYMMDD because in chinese we go 年月日 (year-month-day), and it makes organizing files and spreadsheet entries much more intuitive anyways.