Sentence with doubtful syntax

A sentence that does not seem right on account of syntax

• Not only are verbs largely uninflected in English, but also nouns, pronouns and adjectives.

This sentence seems very unusual although it is understandable. I can't tell what is wrong with it, if anything is. Possibly the adverb "only" is not properly positioned but I can't assert that.

Would someone confirm that there is a problem and explain what is wrong? Otherwise, can someone show that there is no problem?

Not only are verbs largely uninflected in English, but also nouns, pronouns and adjectives.

There's nothing wrong.

As John Lawler points out, Not only ... but also is a conjunction along the lines of "either ... or"

The example equates to

Verbs are largely uninflected in English and so are nouns, pronouns and adjectives.

Expanded further to demonstrate the two coordinate clauses:

Verbs are largely uninflected in English and nouns, pronouns and adjectives are largely uninflected in English.

An alternative view might be

Verbs are largely uninflected in English in the manner of nouns, pronouns and adjectives.

But this does not express exactly the same idea as nouns, pronouns and adjectives can only be considered as an a priori standard.