I haven't pirated any Netflix shows because it's simply too cheap and too easy to just do it legit.
I have the same complaint about HBO Now on the Roku. Man, does it suck.
Lest people think the problem is my network, often when I have the issue I switch to Netflix and never once have I had a problem after the switch. Seems unlikely I just happened to switch when the network problems went away.
But none of that matters, you are correct at this point that Netflix clearly has it figured out and working for you, while their competition does not. Only to say, the dynamic bitrate support is likely to improve on the other apps with time (not to mention, your internet connection is likely to periodically increase in speed for various upgrades to your equipment or your ISPs) so those issues are likely not permanent.
I think Netflix also still uses caching boxes in a few locations, but they are being phased out.
In other words, there are a lot more variables in the equation than just your home network and the Roku app.
Proof? I don't see any indication at https://openconnect.netflix.com/ that their appliance is being phased out.
For me, it's almost entirely that it's easy. Aside from Daredevil and a handful of their comedy specials, I haven't watched any of their produced content, and I'd be just as satisfied if it didn't exist.
If its not on Netflix, its on your preferred torrent site.
I'm got too much to lose to be messing around with torrents. I just want to pay something and get the content I want. For now, that's cable TV, not Netflix.
Anytime I want to, I can go to Netflix and watch any episode of their shows. I ca watch the first season; I can watch the intervening seasons; I can watch the current season. There are no blackouts; there are no embargoes.
I can binge-watch if I want, or I can pace myself, at my pace.
Compare that to the big companies' offerings, where I may be able to watch every episode this season, but not get started by catching up on previous seasons (I know that they hope I'll pay up for boxed sets of those early seasons, but I'll just skip their shows altogether instead), or I may be able to wath previous seasons but not the current one, or (my favourite) I can watch previous seasons and recent episodes but not early episodes this season.
Why would I want to get involved with a show which is such a pain to watch?