How much enthusiasm should we expect over a landing page to test idea?

I was reading the recent thread on de-emphasizing the validation phase in favour of building a small MVP (https://www.indiehackers.com/post/0069e15ccd). A few of the answers centered around the well trodden advice of sharing your idea based around a landing page, and it got me thinking about how the response compares to actually posting a link to a product you've built.

The thing is, no matter how well the landing page communicates the idea, you are not going to get as much enthusiasm - and in turn, sharing and the hype that comes with sharing - as using an actual product.

Recognizing this, I'm therefore confused about how much time and energy into putting into validating a landing page. I currently have 2 landing pages that I've validating. I've talked to a few people and they love particularly one of the ideas more (https://c1rd2wtysv9k.landen.co), and I've had some people sign up as well (should I talk to them too?). But should I stop at 10-20 people, or talk to 100, 1000? Where does it end?

At what point do most people here say "yep, that's enough validation for now, time to build and start testing some features"? ...I find the answer to this question a huge gray area and where I'm struggling with most.

Some people say to find an actual paying customer first, before it's built, and I like that approach because it forces you to concentrate on a revenue model so much more. But it's not always that obvious, especially when your idea may weigh on acquiring some consumer data first.

Sorry if I'm rambling, former lurker and first time poster. :)