> I'd just like to hear a coherent argument why a good product doesn't carry itself to a decent valuation

Why do you need a coherent argument when you can do one better, observing reality. Lots of well polished products flop very hard. Ex: Quibi.

Unless you're tautologically defining a good product as one which is successful (I.e. carries itself to a decent valuation).

> You're doing marketing because you failed at product".

And yet one of the 4 P’s is for Product.

You’d likely benefit from reading through Kotler’s Principles of Marketing.

Ads are a subset of marketing, so I don't really understand how that quote works but a good product carrying itself to a decent valuation probably has some correlation with how good the network effects of that product's user base are and how likely those users are to spread the word. At the end of the day you need eyeballs on your product, and organic growth is usually going to be the slower path(albeit not the worst path for some).

*If you have investor pressure to show growth(usually in terms of user base), you're going to opt for the faster progression.

> you're doing ads because you failed at marketing. You're doing marketing because you failed at product

Define marketing. Is having a website at all marketing? What if I have a private link to sign up for my product, but I have to email people for them to use it. Is that marketing? How can one exist online as a business without doing marketing? If you've ever made a single SEO optimization to a website are you not doing marketing?

What I'm trying to say is that your quote doesn't make any sense. Not only does it fail at understanding what marketing is, it's also just patently false. Great products, amazing products, fail every single day.

I could add them, never used them too.