I got down leveled when I moved to big tech. Spent two years completely remaking the product I was tasked to work on, while the two other engineers on my team, both a level above me, cheered me on and didn’t do much. I turned our product from a total waste about to be cancelled into a promising tech with some momentum, but I spent all my time coding instead of writing about coding, and I likely won’t get promoted aga…
For your work to be easily recognized by others, one usually requires their peers' or manager's support. This means, asking for advice from more senior peers within and outside of your team and talking in 1on1s about the solutions you developed, problems you resolved, and discussing the business impact that the changes will bring product-wise. If no one knows about the product/platform being broken or suffering from performance problems in the first place, then it will be hard for them to value that the product is now working as expected.
Eligibility for promotion highly depends on the product that you are building. If you impact a product responsible for a sizeable portion of the revenue, visibility and impact is orders of magnitude easier to get. Further, the business impact, as defined by KPIs for the product, may need a few months to materialize and show a trend. Unless provided with sufficient observability and historical data, you may not even be able to show that the product is more reliable or stable due to changes in its architecture or performance improvements. Pouring more marketing money may lead to the same effects business wise on the top line (revenue).
Lastly, and most importantly, promotions depend on your manager. If managers are not incentivised for the development and growth of engineers they manage, but more as a function of the scope or size of the team they lead, the latter may be the easier path as team growth may occur naturally with less effort and friction on their end.