I read your comment very clearly, and you're speaking in absolutes like "nothing else matters", "only ever cut back on things like product", "no-one tries to start a new mayonnaise company". And these absolutes simply aren't true.
And sure nobody starts a mayo company but Hellman's is absolutely competing in the same product category with relatively newer entrants such as e.g. Amazon Brand, or Whole Foods 365 brand, on top of other long-existing competitors. My example was directly addressing your topic -- perhaps you're the one who needs to read what I said again. Because according to you, it's inexplicable that McD's is improving their Big Mac by adding sauce.
But just because you don't seem to be understanding my point, let me try one more time with another one of your examples:
> If MCD remove sesame seeds from their bun, there is not going to be a new entrant with more seeds.
Popeye's was winning the chicken sandwich wars, so McDonald's launched their McCrispy. Shake Shack was popularizing better-tasting burgers, so McDonald's switched from frozen to fresh made-to-order quarter pounders. Competition is alive and well.
If McDonald's removed sesame seeds from all their buns tomorrow, it would be national news and they would absolutely lose sales as people switched to Burger King which would probably launch a national advertising campaign about how they've still got sesame seeds unlike a certain cheapskate competitor that seems to have forgotten what makes a burger complete.
A lot of our popular consumer products and foods have reached a kind of "steady state" because they're what people like at the right price point and there isn't much innovation to be had on a yearly basis. There isn't a tastier version of Coca-Cola left to be made. But you're interpreting this as "no competition at the margin" which is completely false. The steady state is maintained because of competition. The moment a company cuts quality to deliver something consumers don't want, the competition will eat them alive (remember New Coke?).
And believe me, I've worked at major corporations, not that it matters though. Please don't throw around insults like someone sitting in their bedroom, it's not for HN. But perhaps you have more of an internal corporate view and are missing the broader economic fundamentals here because of that?