You made an issue with this merger meaning less work. When presented with the solution of Netflix/Amazon you made an issue with the lack of critical recognition. Critics and "sophisticates" form a small audience. Money comes from the mainstream, which watches Netflix and Amazon, etc.
It seems to me that trying to appeal to a limited audience, instead of the mainstream, compounds the problem of content creation due to a smaller level of support from the smaller audience.
Gotcha--
Here's a little more clarity.
You're seeing it as a one to one sort of equation. Lose Fox, but Netflix and Amazon are gaining strength. But that comparison is apples and oranges.
First, the way most big studios are arranged is that they rely on smaller production companies and big name producers to bring them content to produce. Fox proper has made very few films within the auspices of their own development. Off the top of my head, I can think of Singer's Bad Hat Harry, Kinberg's Genre, and New Regency all being there on the lot-- along with at least a dozen other production companies and a handful of big time producers (like Mike De Luca). Some on the lot, some not-- but all have either first-look or overall deals with Fox. They bring content to Fox, and Fox will produce it if the package looks good.
In some cases, like with Genre and Bad Hat Harry, the ProCo's rep and track record is good enough that the studio will hand over some of their IP-- as in the case of both of those two companies working on the X-Men franchise, for example.
Now, say you're a writer pitching a spec script. You go out and take meetings and try to get a production company to option, buy, and/or package your script. On your journey you could go to the Fox lot half a dozen times and meet with completely different entities all working with a deal with Fox. These companies operate independently, and the Fox board above them lets them know if any competing projects come up.
For example, say Kinberg's Genre and New Regency both have interest in picking up scripts about a giant meteor headed for Earth. Fox's development VPs can say to one of the companies, "No, we've got one of those in the works" if one project is further along than the other. Say you are writing that script-- New Regency comes back to you and says there's already a similar property in development at Fox. When they say "At Fox" the mean "with a production companies Fox has a deal with."
As a screenwriter, you can still take that script out to any other production company you like-- but now you know no one with a Fox deal will touch it. But you could find a home for it with another ProCo that decides they like your script so much they are going to push it through quick to beat the other one to market. You still have a chance with your script-- just not back at Fox. Once one studio can no longer do the project, you've actually cutting out many individual potential buyers for your script. Not ONE, but MANY.
I don't claim to know the details of the Disney/Fox deal-- but when you are shopping a script, you have tens upon tens of potential options. When I say Fox and Disney becoming one means less opportunity for original content, I'm referring to this process. I don't know off hand how many production companies have overall or first look deals with Fox, but it's a lot. Disney does the exact same thing-- all studios do. So if there can now be no competing projects between Fox and Disney, and all of their subsidiaries, and individual deals with producers, you're killing off a very large chunk of potential homes for new content. (I don't know if this is for sure happening, hopefully I am wrong).
And keep in mind a "competing project" could be two movies that are completely different, but both of them have a magic pocket watch. A studio head will say, "We don't need two magic pocket watch movies" even if one is a Victorian Mystery and the other is an outer space adventure.
Losing Fox doesn't mean losing just one studio as a content developer-- it means losing several dozen.
Netflix and Amazon are all in one shops, mini studios with their own distribution platform. They don't do what studios do and have deals with multiple sources. They do one of two things: acquire finished products, or producer their own from the ground up. No one has overall deals with these companies. They either buy or fund/produce concepts on a per project basis.
And what I meant about them in the feature space is that while they make features, they are predominantly known for TV style content. They are both pushing, and gaining some traction, but their features do not have the same level of success their shows do, outside of critically acclaimed / high brow entertainment.
Their numbers certainly can compete with TV numbers, but not with theatrical box office takes... not yet. It will shift, but they aren't there yet.