In the regard that she often overshadowed The Doctor, I agree. Female companions for The Doctor should be strong women, and Clara was that for the most part. But there's a reason it isn't called The Clara Oswald Show.
Well, I think it depends. Clara was weak in different ways at different times.
In her first season as "The Impossible Girl," she was a weak link because she was, like, this objectified manic-pixie-dream-girl type character. She didn't feel like a real character, she was the "everything" for the Doctor, as if she were the linchpin of his existence. That was problematic because of how it didn't jive with the Doctor's history. Like, she's been there throughout his entire existence, but we've only known her from Matt Smith's era and onward? And he never said "It's strange...she seems....so familiar to me..." or anything of the sort. It was just a very ham-fisted way to get her into a position of prominence within the show. I thought the story of her origin, and the serendipity of her coming into existence was lovely and sweet, but her role on the show and her importance with respect to the Doctor (especially on comparison with every other companion) was just...off. Rose, for example, was super-important to Ten, but her importance made sense in terms of the characters of the two Doctors with whom she traveled. And although her later appearance was a bit too "super-important" it still was nowhere near the level of Clara's importance. To me, that was a sign of Moffat's fanboyism.
Her second season -- the first with Twelve -- was actually the one I liked the most because she genuinely felt like a character. She was an
annoying character in many ways (because she couldn't decide if she wanted this life of adventure with the Doctor, or a happy home life with Danny), but it worked. They did, however, change her character and said that all of a sudden she's this bossy, demanding figure, which she hadn't been before. Again, weak writing from Moffat, in my opinion. The arc for her character that season, though, was awesome. The cost of the journey is something that's too often not explored on Doctor Who.
And then the Christmas Special happened for that year, and everything went downhill. Clara had lost the love of her life (up to that point). She'd had this very meaningful journey over the last season. It had a real impact on her. And you saw that for, oh, maybe 5 minutes in the opening of the Christmas Special, but then, no worries, she's back to normal, happy-go-lucky adventurer.
And in the most recent season, they changed her character AGAIN from the "bossy" one to the "stupidly brave" one who thinks that life's just a lark. They COULD have connected this back to the trauma of losing Danny...but they never did. The stories never explored that. They never played with the idea that, say, Clara had a death wish
because she had lost Danny,
because she wanted to be reunited with him or was trying to not feel the pain so she got all adventure-junkie on us. They just ignored all of that and she just....became this new character altogether. And in the end, she died. OH WAIT, no she didn't, she survived and gets to be a pseudo Doctor who just doesn't remember the Doctor which would be really interesting and tragic if it wasn't old hat because we saw something very similar happen to Donna.
What's the constant in all of this? What's the underlying problem in all of this? It's not Jenna Coleman, that's for sure. Each new iteration of Clara she played as well as you could expect anyone to. She was charming, lovely, strong, and believable -- or as believable as the writing would let her be -- in each version of Clara. No, the problem is the man setting his dolls out to act out the play he's dreamed up. The problem is Moffat himself. As a writer of individual episodes, he ranges from good to amazing. As a show runner, he's crap.