Why isn't Kindred a popular pick?
She/He has a dash, slow, and DPS. Why isn't she/he a flavour of the month? 
She/He has a dash, slow, and DPS. Why isn't she/he a flavour of the month? 
I think it's because there is a newer champ so in general the flavor of the month group moved on to illaoi.
In terms of ADC picks there was the big rework of 6 ADC's
&
so ADC's have been playing them more.
For jungle
can do really well if they get stacks but if they get shut out of the other teams jungle and can't gank the right targets they start falling behind.
Also got a nerf (though it's a reasonable one) that set a cap to the passive damage they can get on Barron so people playing Kindred are killing Barron slower now which makes the champ feel a bit weaker and makes it feel less like a flavor of the month super op pick.
The last reason is during the All stars event in Melbourne a little while ago which was the first pro tournament on the pre-season patch basically none of the pros picked her. I want to say 1 person picked her and got stomped and no one else bothered, so the people that do Flavor of the month picks off the pro picks are avoiding playing Kindred also...
At least that's my thoughts on the matter.
I hope she never reaches super high pick rates. I don't like furries.
She isn't a bruiser and isn't tanky.
A lot of people (or at least I) highly prefer to play with tanky junglers.
She has really, really strong innate damage skills (E scales with max health, passive gives tons of damage). So great, in fact, that if she was melee she could definitely build Titanic and straight tank and completely demolish people.
Alas, she isn't melee or designed to be tanky, so she suffers from "not being a bruiser" syndrome.
Things become FotM because they have something new and/or overly strong. Kindred has been new for over even a literal month, much less that figurative one and while they have an interesting new mechanic, that doesn't really change or help the fact that they are a RangedAD in the jungle.
Also: Everyone and their mother has a slow and half of their mothers have a dash. ; P
Because there are just better options at the moment
Unless you pretty much neglect your team, or call for help in enemy jungle and neglect objectives on the map in order to stack passive she falls off HARD late game...
So as others have said she doesn't do anything good enough to warrant picking her over "x". Also dat ult it troll yo.
She's pretty popular still (8.4% pick rate), but I think Illaoi is overshadowing her right now.
She's a late game carry. Games don't go to late game anymore