What is the grammatical usage of "but" in this sentence?
You are all but forced to use them instead of standard C++
Could we ignore "but" and yet convey the same meaning?
You are all forced to use them instead of standard C++
All but is an expression meaning almost.
So "all but forced" is like saying "You are not actually forced. However you are urged, encouraged, advised, suggested, persuaded, recommended…"
The two sentences have different meanings, along the following lines:
All but is serving as an adverb in your example, with meaning almost or nearly.