"I keep hearing this, but I never see any of its arguers actually attempt to make a pop song. If it’s so easy, why do only some people have the knack for pulling it off (not the artist/singer; the composer (the person you never hear of))"
Because it is so easy to make, they are making massive numbers of garbage tracks - and it just so happens that some garbage tracks are popular. You need 'garage band' and possibly microphone - that's it. Have a look at how 'Chief Keef' had his music produced by 'Little Chop'. Most top tracks are of course somewhat professional produced.
But consider that 'music' is not the name of the game, it's 'video' (i.e. video killed the radio start), Instagram, twitter, Tumblr and highly visual content. You can see this with Lady Gaga (talented) and SixNine (well, creative, but garbage) - they're at least as visual as they are audial, as are most artists these days.
It's about the brand/image/meme. Someone in their basement, with very little skill, can make a loop, mumble over it, and this 'meme' can catch on. With a very little bit of production effort by a nominally professional engineer, it can sound 'produced'. At least as much of their effort goes into the look, the brand, the relationships, the Instagram, the video etc..
And it's worth adding, the 'talent' that is sometimes evident in this kind of production, may have little to do with the music, and more to do with anything else.
I actually respect the 'marketing' ability, if you want to call it that, of many of these acts. Post Malone has somehow worked his way into having his own festival with his 'Posties' followers. Genius marketing.
When P. Diddy started his label, he would ask his talent scouts "How did they look" - not "How did they sound". Somewhat cynically, P. Diddy was smart enough to know that pop acts are a lot (and ever more) about appearance. A pop artist is like a living brand.
Another feature of 'how modern music is made' is that the producer is now in the creative/driver seat - not the artists. Consider 'TheWeeknd' - his big hit, 'Can't feel my face' was by Max Martin, famous songmaker for Britney Spears and so many others. Without that hit, TheWeeknd would be nobody - we'd have never heard of him. But once his meme/brand was established, he has a 'following' and can churn out a lot of mediocre stuff.
This has always been the case to some extent: Michael Jackson was backed by Quincey Jones - who was Frank Sinatra's arranger. But Michael Jackson is a genius entertainer and true 'pop artists', and of course Quincey Jones is an off-the-hook musical genius producer.
This evident in 'live' music. I've been to countless shows where their music is just some canned track, the artist comes out and mumbles over it? Seriously? In most cases, this is not impressive.
Anecdote: I went to a show recently, bulleted as Brasilian/French/American rap thing in Montreal, I was so excited. The 'warmup' DJ played ... then the 'act DJ' played, a guy with huge fuzzy hair came out, jumped around like a hype man say 'boyeah' 'oi' and whatever into the mike, getting everyone excited ... we were ... anticipating the main act. But that was it!!! No kidding. Some idiot with a microphone, saying a word or two like 'yeah' 'oh yea' 'go go go' into the microphone not rapping or anything. He was passing himself off as an act! The crowd seemed to appreciate it. I thought I was in the Twilight Zone, it was absurd. To me, it signaled literally the end of music: loud, barely audible weird sounds coming out of a speaker, with a fuzzy-haired Brazillian dude sputtering occasional nonsense into a microphone and waving his hands. It's not even Kareoke. It was just noise and hand-waving. This to me is he audial version of the 'pet rock' or the $1M painting that's just a black dot - people can be induced to like anything.
So there are obviously talented pop artists. Ed Sheerhan, a legit musician who purposely writes for the radio. Bruno Mars & Co, are total geniuses. Lady Gaga. Kenrdick Lamar. Ariana Grande has wicked chops, she's obviously a talented singer/dancer/entertainer. Obviously many others, but the charts are otherwise polluted with irrelevant, unlistenable tracks.
Surely some people thought Jazz was easy to make, but I suspect that many were just jealous because they obviously knew they couldn't do it. Jazz is objectively not easy to make. Literally anyone who has tried knows how hard it is. Also, FYI, there's no counterpoint ... but the chord combinations, the speed of the changes, the variety ... is far more than in most forms of classical music.
Most pop music is very easy to make, and there are mountains of gibberish there for anyone to sort through. Fewer and fewer gems.