Get over it. 'Day' is a perfectly reasonable way to express '24 hours' or however many layers you want to digress through.

'Day' can also mean from midnight to midnight (or perhaps closer to from 4am to 4am when talking about perceived days not statutory days) or just from around dawn to around dusk or how long it takes a planet to rotate.

Even less common is using 'day' to mean 'from time X to the next time X', which you appear fixated on claiming as the only valid definition of 'day'. Just look in a dictionary and you're likely to see many mentions of "24-hour" and I doubt you'll find any mention of what you've defined.

The scenario you paint to justify your definition is quite strained but also illustrates an important point. Using 'day' for duration implies relative imprecision. No one would jump from 'takes a day' to 'takes exactly 24.0 hours'.

The fact that sometimes Sunday lasts 23 or 25 hours isn't a big deal for normal folk. But I find it makes more sense to realize that sometimes Sunday isn't quite a full day in duration and sometimes it is a bit more than one day in duration. Sure, it is still exactly one Sunday. But 'day' doesn't have only one meaning. Sunday is one statutory day, but is not exactly one planetary rotation (a 'day') and sometimes isn't 24 hours (a 'day' in duration).

Similarly, sometimes it takes more/less than one minute for the clock to go from 12:00 to 12:01. The clock reading doesn't define the duration known as 'one minute'. One minute is simply 60 seconds. If I move the hands on the clock around for whatever reason, it doesn't cause 'one minute' to become longer or shorter.