Presumably you're not accusing "open web" activists of having ideals that favour inhibiting bandwidth, or hosting content on slow servers, so noting that proprietary ["closed"] services had those facets is irrelevant to your original comment.
If you felt that people wanting to use PNG, because GIF was closed and contrary to [the nebulous concept of] "open web ideals" has retarded progress on the web, then that might be an example? I'm struggling for an example, because I don't know of any examples, which is why I asked you because you spoke implying you know [many] examples!
Flash made online video work. Facebook & YouTube made contributing & sharing content accessible. IRC, host-your-own webpages, later attempts like RSS and such, which were more idealistically "www" were also not right for Aunt May. They were right for 1990 users, who were a self-selected bunch.. not alway representative of the majority.
Even jewels like Wikipedia (a brilliant achievement of the www idealism, imo) are relatively inaccessible (the editting part) to the average person. That works very well for Wikipedia specifically.