I don't hate the Tiguan, but on paper - it's just not competitive enough.
1) It has no hybrid/electric option, whereas bestsellers such as RAV-4 and CR-V have been offering at least a hybrid option for several years.
2) Weight / power ratio is one of the worst in this segment, despite having a turbocharger, that budack cycle engine is just not responsive enough, and the car is several hundred pounds heavier.
3) MPG is one of the worst, as it is one of the heaviest entries, it's not surprising to have crappy MPG.
4) Other entries usually offer more cargo space, or overall practicality is better. Especially the first gen Tiguan sucked so bad.
5) Resale value (at least in Canada) is bad, people buy cars based on the resale value.
6) VW models always have "sterile" interior design including the Tiguan, but typical SUV buyers look more rugged/versatile design - lots of big cubbies/storage compartments etc.
7) VW, as a brand and model range, is a more suitable brand for EU buyers. In North America, If you want reliability - you go with Japanese, if you want value - people choose Korean, if you want prestige - you go with Audi/BMW/Merc etc. VW could not offer anything to stand out with the Tiguan in North America. If you ever sit/check the EU models, they almost feel like an Audi, but here they couldn't offer same level of quality.
8) VW just don't have a good reputation after the emissions scandal, and many buyers steered away from the brand because of it. I think that's the main reason of the hate in the last few years.
The only unique feature was 7-seat option, but I think they don't offer it anymore. I also appreciate the fact that they are not using a dual clutch, or a CVT in an SUV, I'm glad they use Japanese Aisin 8 speed in Tiguan, that'd be the reason why I would've bought it (instead of something with CVT) if I was looking for a car in this segment.
Overall it's not a bad car, but it is just not the best in any category.