This is actually a really interesting response. This was the topic of several large threads recently and the consensus here seemed to be that there was no consensus on what a 'traditional playstyle' was. The opinions seemed pretty entrenched either firmly in the sandbox, or in opposition to the sanbox as the 'one true way'. I'm probably not being fair to either side there, but you get the drift. When you say 'traditional playstyle', what are you actually indexing?Not irrelevant but certainly being overly stressed as a solution to the problem of difficulty GM'ing in a traditional playstyle when it's instead a preference for a different playstyle.
In other words improv as opposed to planning sessions out isn't a solution to making running a game easier unless I prefer improv/am good at improv, don't have anxiety, can think quickly on my feet and it won't degrade the quality of my game for my players. It's not solving the problem in the context of the game most people are running/playing (which is traditional D&D)... it's basically stating go play a different game... which yes IMO isn't all that helpful for the vast majority of people trying to come up with an easier solution.
EDIT: If anything this is the solution for people who don't like D&D not those who enjoy D&D and want to have an easier time running it.
As to your second point, I have played and am familiar with many, many, different RPGs. There are a bunch of non-D&D games that I love. That said, I probably spend more time mining them for ideas to port into D&D to fix problem X or Y than I do playing them. That's mostly because where I Iive I don't have much (any) choice about players, and D&D is what fits. So I hack bits and pieces off the other games I really like and bolt them on to D&D in ways that I think are interesting. That's why those games are relevant even to people who only play D&D. Everyone (many people?) eventually get tired of the current D&D edition's take on X and wants something different. Not a different system, just some hacks or homebrew solutions to those little rough spots in the rules that keep catching your attention.
And yeah, this includes everything from playstyle down to little bitty rules hacks.