Talking about Google: what's missing is, things that used to work now don't work. Like "+", and verbatim searches don't always include every word. If you try to do more advanced searches, like using "intitle:" etc, after a few tries you have to do a Captcha each time. At least, I did last time I tried, a couple of years ago. (Thanks to using an old Mac + old browser, I never see any ads on google, but understand that's a problem for people too.)

Contextual search.

For example if I search for a movie, then a bit later I search for a person, the SE should 'know' that the person I'm looking for is an actor in that movie and give me relevant results, not completely unrelated random people. That's beyond trivial to do.

Also removing all 'popular' results from link farms and pop culture sites, excluding entire categories for example searching for a mythological figure should give me results from *.edu sites, not weird ass anime sites etc (and Googles filters no longer work properly so you can't drill down in queries anymore.)

I think the market is ripe for a new product that does what Google used to do before they abandoned their core competency (and DDG is a joke and doesn't count)

1) API (to build search agents, complete tasks etc) 2) domain specific search 3) string match (I don't like semantic matching) 4) structured result with Facets

Blacklist is certainly missing. I want to filter out garbage sites that somehow hacked the SEO game.

Who should curate such a blacklist though?

I think it should be a blacklist I as a user can edit and contribute to.

Although if it's exportable, perhaps you can make importable list of blacklists curated by other people too.