Threads like this come up fairly regularly, I'd guess about twice a year.
In the years I've been on this forum and read people's complaints I've come to this conclusion: FT isn't aimed at me anymore and I don't think that's necessarily a bad thing and the reason is two-fold.
First: Flite Test has always been about drawing new people to the hobby and getting them started. At first is was educational content with the occasional big build to draw people in. Now they have a large archive of video and other resources to help people just starting out, so the content has shifted to more impressive feats to grow interest and draw people in.
Second: I am not a beginner. I have flying experience. I have building experience. I love doing scale details. I love working with balsa. My income and thus my budget has grown. I have researched aerodynamics more in depth than any 20-minute FT video would ever try to go.
So, when they make a mailbox fly or build a plane I could never fit through a doorway much less get into my car, I watch. I enjoy what they do and then I keep doing whatever it was I was doing. Their content doesn't really engage me anymore because it's not meant to.
I've said before that I want FT to grow with the people they've brought into the hobby, to show when and where and how to improve. But if they did that they would risk leaving behind all the potential new pilots they could still bring in.
Over the years I've decided that it is better they keep reaching out for the newbies and let those of us who are already hooked find the next step ourselves.
Do I wish they still had content aimed at me? Definitely. Do I wish FT had some more in-depth discussions of the build process? Sure. Would I like them to explore different build methods or tips on fine-tuning your flying skills? You bet!
But in a way they don't have to, because that is what I can come to the forums for. FT hosts these forums so that we can explore, educate, grow, and share with each other once we learn the lessons they have tried to teach.
TLDR:
I get the disappointment; I feel it too. Now it's up to us to be the change we want to see in the community.
Just my 2 cents.