If your product needs a tour your product is badly designed.
Imagine you walked into a convenience store and the owner was like "Hey you need to take the tour first!"
The best UI is no UI at all.
I can't think of a single time I've looked at a product tour and thought "well, I'm really glad they told me that, I never would have figured that out.
What the product tour I think often misses is that people don't want to learn your entire tool at one time.
They came to do one thing, that one thing needs to be brain dead simple.
Over time, you can show people what else they can do. But a product tour isn't the way to do that.
I think progressive UIs where you expose more and more to the user over time is the way to go.
If you're thinking "but I have so many features and capabilities this person needs" you probably haven't identified what the one thing people are paying you for is.
UI is like a joke. If it needs explaining, it's bad.
That's why I like startup tips.
"Did you know that in California all gas stations are required to provide you with free air and water for your car?"
I chuckled cause the convenience/grocery store is laid out to make us find the high margin items and not what we need. They can't explain it to us otherwise we'd shop less.