I don't see how any of this is specific to Google. Everything you've said here is how companies function. If you want to work on things that are not important to your manager, why should you expect anything? And bad managers exist everywhere.
My point here is that my managers thought the latency of Google Maps was important, doing good work on it got me promoted, it was not a product launch, and things like this are happening all the time across the organization.
I disagree. Add a couple of these features, put them behind an experiment flag, and inspect metrics that matter. What usage are they getting? Do users in the experiment use the product more frequently? And for longer periods? If not, perhaps feature parity with Excel is not the highest impact project, despite the feature requests. If you are finding it hard to come up with measures that show impact towards your orgs' OKRs, this is also a signal that your pet project may not be the best thing for you to spend time on in the eyes of your bosses.
At a high level, promo is an incentive that directors and VPs use to keep an org working towards strategic goals. You may disagree with those goals, but that doesn't necessarily mean promo is broken.
During my interview process, my recruiter was very much my advocate. Have you talked to them honestly about this? It should not hurt you. I'm sorry you're going through this.
I've been at Google for 12 years, and this has not been my experience. While it is a popular narrative, it is by no means dominant, and is fairly specific to individual teams. I got my second promotion leading the Google Maps Desktop Latency team. We demonstrated impact solely by reducing load latency and increasing performance while advocating for latency consciousness across the product space and implementing latency regression tests and monitoring. Google has some of the most complex infrastructure in existence, and there are thousands of engineers that are getting promoted and finding gratification in maintaining and improving this infrastructure.
My experience at Google has been characterized by collaborating with the smartest and most driven people I've ever worked with. And I worked at several companies before Google. I think a side-effect of this personality type is that the engineers themselves want to make a difference, whether through maintaining Google's complex infrastructure or launching new products. And while it may be easier to show impact by launching a new product, it is by no means a problem unique to Google. Startups find it much easier to show impact by launching and buying users, rather than measuring how useful the product actually is.
I have come to believe that, lean-startup style, a good engineer should be able to demonstrate how the work they are doing is important to a company, a product or a product's users. With a little bit of thought around how to show that the work you are doing actually is valuable to your organization's OKRs, you can get promoted doing whatever work appeals to you the most.
I think the weekly post idea really applies to the reader, not the writer. Perhaps you could get around this with a "digest" style of posting. I.e. I can write as many posts as I want, but it will only be published once a week as a digest of posts. This might fit better with human behavior too as it lowers the cost of a single post while still achieving the goal of updating friends on what's happening at a spaced interval.
My point here is that my managers thought the latency of Google Maps was important, doing good work on it got me promoted, it was not a product launch, and things like this are happening all the time across the organization.