Personally while I feel that Kindred can carry pretty hard if the need arises, Kindred also needs to do quite a lot more before they reach that point.
You are heavily, heavily reliant on two things 1) that the enemy team isnt contesting your marked camps and 2) that your team can work with you on your marked targets. 3) Your team knows how to work with your ultimate.
Without marks, youre incredibly, incredibly screwed even with items. You really need to start hitting 8-10 marks before you start to really kick ass, which can be pretty difficult in most games, as free marks on camps are harder to come by when you hit higher up, as only baron and dragon become marked. You also dont get to build as much crit as other ADCs, because you're jungler and there are other items you need more (unless its super late game where you can sell your jg item for like, I dont know, essence reaver, because its crit, 10 more AD, and more CDR and red smite doesnt see much use when that extra tiny bit of true damage/20% damage reduction probably wont save you in those 40 minute plus teamfights).
If your team cant work with your ultimate (say for example, a xayah ults then uses rootcaller while the enemy is already at the 10% threshold, or a lux Es while theyre still invincibile, is the most common issue in my experience) then that can make or break a teamfight, because it affects both enemies and allies. If your team can burst enemies down after your ult ends, then great. If not...ouch.
So IMO, Kindred can carry pretty hard. They aren't really a hyper carry however, IMO because of their lack of consistency. Some games you'll just get screwed out of marks and you're boned. Vayne or KogMaw just need to get items, while Kindred needs to rely on and juggle more things to be effective.