Laptops are not unpopular devices. People use them at work, at home, to shop, browse, everything. People love their laptops. At work, people love dual monitors etc. That won't change because humans need sufficient screen real estate to get stuff done and display documents etc.
As I said before, quality of users is also important. You should analyze your traffic to see bounce rate and spending for mobile phone vs everything else.
You seem to think that a mobile layout will be "compromised" if the design starts with the full website layout. This is old thinking. If the brief says "we want a strong website on all devices" then your designer and devs will make sure the site is great on all layouts. Otherwise they're not doing their job.
There's no universal law that says unless you design for mobile first, it will suffer. Your idea is left over from years ago when mobile phone usage was low, and mobile browsers were poor. Remember when there was a delay between pressing a button and the action, because iOS was "waiting" to see if was a double-tap or not. The compromise was built-in.
Add to that the crippled cache and memory abilities of phones, and the preference of mobile manufacturers to push people to native app stores, nobody should be surprised that mobile browsing was/is compromised by its very nature.
There’s some variation depending on the demographics e.g. sites with a large audience amongst the older population tend to have more tablet, and laptop visitors.
You can check the mobile vs desktop split for most sites using the Chrome UX Report
You say my logic is flawed but too many sites are designed with large screens in mind and then retrofitted to mobile with poor outcomes for the user experience
Starting with a big screen design might allow “all possible features to be clearly realized, sorted, and refined” but all too often it leads to unoptimized mobile experiences because compromises are made to make the desktop experience adapt to mobile
And when 75% of the audience aren’t going to get that full experience I argue that designing a great experience for the 25% to the compromise of the 75% is a flawed approach