Jose wrote:

True. My issue is "your only alternative is to accept the new clearance
or cancel IFR", and "You've accepted the clearance just by reading it
back."

So if you "accept" a clearance and then figure out you don't like it,
what happens when you try and change it? Does, in real life, ATC refuse
your request to change or do they really insist that you, for example,
climb into known icing conditions in your uncertified airplane?

In other words, is ATC really mean and uncaring? Never happened to me,
but my experience is limited; every time I've asked ATC to help me fix
something, regardless of whos screwup, they have been reasonable.