I'd say moving to a different company/team every few years is a very useful way to keep oneself motivated. I personally make it a habit to look for different opportunities every few years. Even if I decide not to move after evaluating options, it helps me keep motivated. And when you do move, there's nothing like the excitement of learning new things and feeling a bit nervous/anxious in a new field and having/wanting to prove oneself that will keep you motivated and focused.
As for "moving protocol buffers" - indeed, all code does, at the smallest level, is just moving bits and flipping bits. There's no amazingly interesting things in computer science when broken down. What's interesting is what happens in between and what the combination of all of those accomplishes together. What it accomplishes is what matters. We're all just standing on top of the shoulders of giants that is collective human knowledge, adding tiny bits of our own contributions on our luckiest days, and just barely holding onto the shoulders in our normal days. If you're not advancing human knowledge, keeping some tools used by millions working is useful and meaningful. Keeping millions of people entertained is useful. Providing tools for other thousands of engineers is meaningful. The meaning of a job is what you define it to be.
Even if you decide you won't find meaning in the job itself and decide to take it purely as a "to-make-a-living", necessary-evil endeavor, what you achieve through it can be personally meaningful (provide for your family, for your personal experience, for society, etc).
The meaning is what you define and draw from. Even the job of driving a garbage truck has a meaning. Software is no different - short of doing something actively harmful or you are morally against, you can find a meaning in any job. It may not satisfy your ambition or ego, but that's a different problem that finding a meaning.
By that standard, practically all other companies are failures, since practically all other companies pale in comparison to Google search. So I would say your claim is absurd.
I don't know how old you are, so it's hard to tell how long ago you're comparing. But how do you know if this isn't simply because there are a lot more content than it used to be ?
I had no idea what Yices is. So I Googled it - the first link is SRI's Yices SMT solver. I tried "yices alarm" "yices signals" "yices timeout", and all of them showed only links related to Yices in the first result page (various manual pages, types, etc). So my attempt at reproducing your experience has failed.
It's still there on my Chrome desktop or Youtube app on android.