Is a home theater even worth it or doable?

Oh hell yes. However I won't bother going past 5.1 setup in my smaller setup 55" monitor.

I agree, a lot of streamed content sounds better when I switch the AVR to 2 channel.

Blu-Ray/DVD programming separates center channel info, that is just missing if you don't have center channel speakers.

rear, just loud enough that you are unaware until you turn them off. Black Hawk Down, they are key in many scenes.

Sub, I keep it low, but it kicks in for Jurassic Park.

Most people (people not nerding out here on an audio forum) can enjoy a good home theater and most people spend more time watching TV and movies than anything else. Streaming a movie, or playing from a BluRay disc doesn't really matter, a decent system makes both enjoyable, and many people will never know the source unless you show them a disc or bore them with talk about streaming, and they still will tell you they sound the same. Focus more on the basics, like a good center channel as that is where most of the sound will come from for video. Get decent mains, and that is where the other important sound will come from for music and video both. Definitely pre-wire the room as much as possible if the walls are open, and keep in mind that most minor imperfections in sound stage from surround speaker placement can be adjusted from the surround processor. Get a decent processor/head unit that also allows you to play 2-channel stereo in some type of "pure direct" mode. Keep in mind that you may be the only one that is even concerned about having good sound in your circle of family or friends, and in my case not a damn one cares about the details of my system or spends time doing any critical listening.

"Netflix, HBO Max, and Hulu. "

what about Apple TV, Showtime, Paramount, Prime, AMC, BritBox? Get your subscriptions in order first! :)

Not sure what your "open concept" space allows, but I can suggest a few things from my experience. We are fortunate to have a semi-dedicated but all-purpose family room that can be darkened with shades for projection TV. We use a 105" inch retractable screen and a Sony 4K Laser projector. The picture is great, but the decent sound system makes it even better. We use Apple TV > pre/processor > 5-channel surround amp > subwoofer. rear channel speakers are flush in the ceiling, basically invisible. Center channel is not visible but concealed in fabric-fronted cabinet below the screen.

Since you are apparently still working on your renovation, now is the time to install good sound equipment and discrete wiring. I also recommend soundproofing your room. We used RockWool brand insulation in all walls and ceiling.  This makes a nice difference and allows others not in the home theater to carry on without distraction.

Good luck with your project.

I’d recommend having at least a 5.1 setup, but I’d wire for a 7.2 system since it’s very cheap while the walls are down and gives you the flexibility to expand later if you get the itch.  Especially with an 85” screen you want the sound to match the scale and immersive qualities provided by a nice TV that size.  I once did a home install where the guy invested in a nice $20k surround system but would only buy a 42” TV because he wanted it to fit in his damn antique cabinet.  The sound was so much bigger than the impact of the TV it was a mismatch from an enjoyment standpoint.  As with everything in audio and HT, balance is key.  Best of luck.