I do not formally know grammar, but I can pick out three subject-verb constructions in that sentence.
“It” and “is”; “one” and “must”; and “we” and “have.” The last two are separated by a clause (at least, I think that’s a clause there between the commas).
That sentence is of the long and convoluted type that I often find myself writing. In most cases, however, I go back and break my original long sentence into shorter, more easily managed, chunks.
In a good sentence, there will be a clear subject and verb, to which subordinate clauses may be attached. The example sentence does not have a clear subject and verb. The pairs you mentioned are all “pronoun + linking verb” sets, rather than true nouns or verbs. That is one of several reasons it is a poor sentence.
One of my sons writes long, compound-complex sentences, sometimes with multiple semicolons. That style can be effective, but it’s easy for the point to get lost. I encourage him to break them up, not because they are incorrect, but because his teachers want to read a paper quickly to assign a grade, not at leisure to enjoy his style.