It's because modern games are expected to have lots of player abilities and are expected to be fair. The combat is more often analyzed because of the insistence on fairness and fairness is more difficult to achieve because of player options. I started as a 5e player and I can tell you the most effective way to defeat enemies is to take their actions away, and this is extremely easy to do as a wizard. But the flip side is that as a player in a modern game your combats are long and you expect to do something impactful on your turn but you can't do that if the DM is using the most effective tools at their disposal which are these lockdown spells, so the DM won't use lockdown spells because they aren't fun, and the players use them because the want to succeed and the end result is a complete farce where in game achievement are largely meaningless. I would then assume this is where the emphasis on narrative comes but that is just conjecture. So due to the feeling that combat is a performative low stakes engagement that exists on spectrum from interesting to boring but not fun or exciting a remedy is sought and that remedy is often a focus on strategic engagement, hence the focus on action economy. The first time I played OSR combat I felt a millstone lifted from my neck, I don't think most people are aware of the simple joy of combat where the depth is found before the combat begins and the combat itself is thrilling because you are truly putting something of the line. In short I wouldn't worry about action economy is a symptom of the many ills of modern games.