Well, agree to disagree I guess. I'm more then halfway through Barbara's run and she's done literally nothing iconic, she honestly rarely reaches the level of useful. She's the motherly figure of the group, and occasionally she gets captured and needs to get saved. But there hasn't been a single story where The Doctor actually needed her to do anything, unless its to fix a problem she caused like in The Aztecs. There was also Planet of the Giants, which had her poison herself, realize she'd poisoned herself but then hide it from everyone until she collapsed causing everyone more problems. She also managed to kill an innocent creature in The Rescue even though Vicki gave her more then enough warning to not do it. Really, it seems like when I remember something that Barbara did its almost always something negative that caused trouble.
As for her acting, its standard 60s stuff. She's fine, but both character and acting wise like I said I'd put her in the middle of the road. I don't really think about the quality of the acting in Doctor Who unless its absolutely terrible anyway, and the main cast of Doctor Who almost never gets bad enough to be notable. That said I also don't associate Louise Jameson with particularly great acting (although I like Leela a lot), so we're obviously judging things from very different perspectives
If Barbara and Ian weren't the first companions they'd be on the same level of forgettable as companions like Ben & Polly or Victoria, where there is nothing really wrong with them but they have nothing particularly noteworthy. Even Dodo at least had being a weirdo and having a terrible exit to make her memorable. But being first is important as well, I'll never argue that Ian and Barbara weren't important, and again I don't dislike them, but I'll never list either of them as the highlight of a story.
The 2nd Doctor's era would be the start of companions really coming into their own in my opinion, with Jamie being one of the greatest companions ever and from there every Doctor afterwards (at least in the classic era) having at least one great/memorable companion if not more.