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Screen sizes are extremely fragmented and will only become even more so, necessitating fluid designs that can adapt to any viewport. Sorry, but if businesses tried to appease the average reddit neckbeard, they would go bankrupt.
Think I'm wrong? Guess my screen resolution. I'll give you three tries.
I'm a front end web developer for a platform that offers mobile and desktop views. You're right that it's a direction things are going in. Two insights I can offer:
1) Designing mobile and web completely separately takes up a ton of time and resources and most web teams (ours included) have a giant to-do list of things to make so anything that saves time is favored. 
This includes designing layouts that are similar between each (heck we have some designs that just adjust layout based on screen size doesn't even bother explicitly checking for mobile vs not). So whatever layout is chosen it's really likely they'll be really similar.
2) When designing, we are told it's a good design principle to start designing for mobile first, then adjust to web. So yeah things look even more mobile esque these days.
No comment on your opinion really, I don't have a strong opinion on it myself personally. Just verifying that in my work experience mobile esque design is becoming more of a thing. >

This.  This entirely.
Sprinkle in the internet's tendency to be an echo chamber where trendiness matters more than uniqueness, and you get what you get.  Everything looks the same. >

I think mobile devices like tablets and phones have overtaken desktops to browse the web, so it's natural to accommodate this shift. That being said, good web designers create visual layouts for various screen sizes and orientations.
What's really annoying to me nowadays are all the damn prompts to accept cookies. >


What's really annoying to me nowadays are all the damn prompts to accept cookies.

Thank the EU for that one.  Websites cannot collect your information without your permission, so they now ask if you want to accept cookies in the most annoying way possible so you just accept them taking your data. >

Just be a Gigachad and take 15 seconds just to decline every time >

Personally i cannot be damned and just install "i don't care about cookies", i am not really bothered by those pop ups anymore >

Every time they change IMDB it gets worse. >

Fuck infinite scroll. >

Apparently macOS design team was merged into iOS design team also. >

What you are seeing is mobile-first design? Like there's this one big picture and few text on the screen at a time?   
Just like you OP, I hate it too. I prefer the desktop first, with nice one or two sidebars, that automatically goes to the bottom or hides (until you click on an icon) when the screen size shrinks. Even WordPress themes shifted to that design as of 2017 I think. That's one reason why I stopped my web development freelancing.  
Now, I wonder if there's still market for desktop-first design? Hmmm... >

The day they get rid of old.reddit is the day I'm done with reddit forever >

Yep.  The dumbing down is the result of marketing to the dumb masses >

Dumbm asses. >

The internet is just going downhill. At least we have Reddit. >

Tru... Everytime I go on mobile it always seemingly for some reason is better peformance and has more features. Just sucks. I like using my pc more but everything on pc is turning into mobile. And windows 11? *cough* Hell no im not upgrading to windows 11 ever.