It looks like storytelling stuff has been taken over by HOGs, VN and walking sims. Nothing wrong with those genres, but it is a bit hard to locate the "pure" adventure games. Those are the recent ones I found:

Detective Gallo -- Cartoonish whodunnit.
The Raven Remastered (a remastered thing. Guess it counts too)
The 25th Ward: The Silver Case - not sure what this thing is???
Lake Ridden - one of those 1st-person-no-one-else-around things that Myst made popular.
Unavowed - high-res pixelart in this one.
Unforeseen Incidents - I really like the ink here!
HIVESWAP: Act 1 - good stylized 2d animations, based on some webcomic. Hope some more acts are coming.
Solo "Solo is a game about love. About love as fuel" -- now THATS an interesting gameplay mechanic!

Gog also relaunched a lot of classic adventure games recently.

Lamplight City is launching on September 13th. A detective mistery with several cases to solve and gorgeous old-style graphics.

Thanks -- That one looks pretty good!

I always thought HOG, VN and walking sims ARE storytelling stuff. Maybe you meant puzzlesolving stuff? Since classic adventure games are about overcoming some intricate obstacles and getting out of peculiar situations, as much as telling stories.

Only 2018?

Repentant
Rusty Lake Paradise
Odysseus Kosmos and his Robot Quest

Revolution are meant to be doing a new game. There must be of plenty good Pre-2018s you haven't played yet though

There are adventure games without stories, like The Manhole, and there are stories without any kind of puzzles, like kinetic novels.

It's very blurry where the exact genre borders are. Personally I do think that "storytelling stuff has been taken over by HOGs" sound a bit strange, because HOGs have very thin storylines and finding bicycles on the Moon doesn't in any way connect to the paranormal murder mystery or whatever the subject matter is. Visual novels and walking sims are more likely to fit that description, but at least visual novels come from a completely different family tree of games, and historically originate from a different continent even, so any connection there is kind of virtual.

Now, as for the original question about new "pure" adventures, there are some coming all the time. Although what is a pure adventure? I guess games like Hero-U don't count, even though it comes from one of the best-known adventure game designers (The Coles).


Some of the most interesting titles that have been released this year are (and this is only my opinion, and for the record, I haven't had a chance to play any of these yet...):

Cosmos Quest IV

http://www.adventuregamestudio.co.uk/site/games/game/2235/


Big Trouble in Little Imola

http://www.adventuregamestudio.co.uk/site/games/game/2279/


A Rite from the Stars

http://store.steampowered.com/app/792370/A_Rite_from_the_Stars/


Unavowed

http://www.gog.com/game/unavowed


Odysseus Kosmos and his Robot Quest: Episode Three

http://store.steampowered.com/app/645820/Odysseus_Kosmos_and_his_Robot_Quest_Adventure_Game/

etc. etc.


There are also many titles which may, or may not, come out this year, which are in the adventure context noteworthy releases. Such as SpaceVenture and Leisure Suit Larry: Wet Dreams Don't Dry.
Also some of the more indie-like games, like Gibbous. http://gibbousgame.com

Saint Kotar is due out and looks interesting