I think many are missing the point, citing arguments about the old guard and protectionism.
Watching on a small screen is a fundamentally different experience, even on a 55 inch screen at home. And bear in mind that a good part of Netflix viewing is not on 55 inch screens, but smaller.
The example of Roma is quite telling in this regard. Those who saw Roma in the theatre tended to really like the film, whereas those who watched at home were left puzzled or bored by it.
Technology always affects the art that is made - we've seen this in music with the transitions from LPs to CDs to MP3's and downloads, which has undermined the album as a creative concept.
We also see this clearly in TV with the series dumps that some streaming services employ. While it's great for binge-ing, you've started to see some commentators push back against this model. The better programmes with more ambitious stories benefit from giving audiences some time to ponder the narrative, for the story to breathe. And a drip feed means they can be part of the broader cultural conversation for a couple of months, rather than 1 week.
So yes, there's a bunch of upside to new forms of distribution etc, but when it comes to films in this case, some creators are pushing back, and while it's easy to dismiss them as victims of an old mentality, the ones who are voicing concerns tend to be those whose films suffer by comparison on smaller screens.