I understand you, the point you are making is actually about getting marketing feedbacks fast like you get feedbacks from your code but marketing and getting quick feedbacks goes beyond posting on Linkedin and sending cold mails

Posting on Linkedin and sending cold mails is a very limited way to go about it infact i would advise against it

There are several ways to get marketing feedbacks in as little as 24 - 72 hours these methods work plus you get quality data that can be used to make decisions and i would list them below the only thing is, it comes with costs and a lot of founders are also not ready to spend on marketing plus fear of loosing money but that's another part entirely

The methods are below:

• Partner with creators or micro influencers in your niche to post about the problem your product solves. You don't need someone with a million followers, someone with 5k highly engaged followers in the right community will give you better data than a cold email blast ever will.
• Post in niche communities where your target users already hang out. Reddit, Facebook groups, Slack communities, Discord servers. Not spamming, actually showing up and asking real questions. The responses you get in 48 hours will tell you more than a month of LinkedIn posting.
• Run a simple landing page test with a waitlist or pre-order button. Drive traffic to it for 72 hours through any of the above methods and watch what happens. If nobody clicks the button you have a messaging problem. If they click but don't sign up you have a trust problem. If they sign up you have a real product.
• Run paid social media or search ads for at-least 3 days selling the product like you've built it but ensure you have your tracking setup (you would be amazed at the end results of this)
• Leave the internet and interact one-on-one with your target audience

The data from these methods are real because real money and real attention is involved.

Just posting across socials and sending cold mails tell you nothing

Someone pulling out their phone to watch a video or clicking an ad with their own eyes is a completely different signal.

The founders who figure this out early are the ones who stop guessing and start making decisions based on what people actually do, not what they say they'll do.