Instant search was easily the best thing about Opera. Honestly, what's the difference between any of the modern browsers? That it was discontinued "because not enough people used it" speaks to how decisions are made in developing software these days. How many people are enough?
It's the same reason I can't move the hamburger menu in Firefox from the right to the left, and why the Lightning extension sometimes vanishes when Thunderbird is updated. Software is developed to make it easier for the developers, and not the users.
An Instagram extension? Who is kidding who? How many Instagram users use Opera?