Huh? Someone playing a B/X clone and someone playing 5e are not playing very different hobbies. They are both playing TTRPGs, and both playing D&D. It's literally the same hobby, as the word "hobby' is defined.
It would be like arguing that someone who has a hobby collecting matchbox cars has a very different hobby than someone who collects Hot Wheels.
Well, yeah. It's not like they have shared best practices, or can meaningfully help each other to achieve their goals. And, well, collecting different things are different hobbies in my book. It's not like I, while collecting firearms, can meaningfully talk to a hot wheels collector beyond the way I can talk to someone interested in, idk, tango dancing. Sure, we can talk passionately about our things, and it may be a very fun conversation, but we wouldn't be able to exchange experience in a way where we learn something applicable to our hobbies.
And, to take a step further. TTRPGs are literally table-top (well, sure we have VTTs, but there's a Tabletop Simulator). Can you give a meaningful advice to someone playing Munchkin, or, hell, chess? Can they give you one? Sure, they can give you some cool ideas, but that's not that different from watching a documentary on butterflies and getting cool ideas from there.
Old school (where players try to overcome fictional challenges with their wits, with the GM being an impartial judge) is very different from Mid school (where players are going through an adventure path, with the GM being game designer, narrative designer and level designer), which is very different from New school (where the players actively work together to create a cool and engaging story, exploring a theme and basically having an allegorical debate on real-world subjects, with or without a GM). There are barely any shared best (and words) practices, other than not being a dick and bringing snacks with you.
If one would try to approach a New School game with Old School expectations, like "oh, that's a TTRPG, I've been playing TTRPGs for my whole life, this is basically the same thing", they would end up being disappointed (and possibly leave others disappointed too). And vica versa, yeah.
If one would try to approach a New School game like a separate entity, they wouldn't have the same problems. They may not like it, for one reason or another, but they wouldn't be frustrated when familiar patterns don't work. Or maybe they will like it, for other reasons than what they like the Old School for.
Jumping into the analogy land, if I'd try to play Call of Duty (an arcade FPS) the same way I play ArmA (a military simulator), I would have very bad time -- because Call of Duty and ArmA have almost nothing in common. Yeah, I move with WASD and I look around with mouse, and R is a reload key, but other than that, they are just... Incompatible.
It doesn't mean that we should grab our rifles and defend our hobbies from outlanders or whatever. It means, that it's valuable to embrace the differences, and leverage them.