I’d say it started at a 6 or 7, and grew to a strong 8 over its runtime. Most of the characters have always been beautifully nuanced, but the stakes of its plots have always been unnecessarily inflated, and the endings for each story arc are of very mixed quality. After the jump to the 31st century, the storylines became much more Star Trek-ian, and the show started to display more of its own identity separate from classic Trek and action movie tropes, and that pushed it into properly great territory.