Have you over-cooked the first draft of your novel?

My first draft was full of errors. There were too many characters which I reduced to eight, which is acceptable, although five or six is the norm for most genres of novels. By characters, I mean those whose presence will be virtually continuous throughout the novel.

I received two qualified literary opinions of my first draft. They both drew the same conclusion. There were at least five or six novels in my first draft, and too many characters leading me astray.

I had the beginning, middle and end to my main plot and storyline, amongst other storylines. The excess of characters led me off on unnecessary tangents and took the focus off my protagonist.

Things became much clearer when I reduced the characters and concentrated on one main storyline and one main outcome.

I wonder if trying to cram to much into a novel is a common error?