I've even heard jokes calling Season 8 and 9 "The Clara Oswald Show featuring The Doctor".

This has pissed me off ever since it originally became a meme around halfway though series 8, and then became unjustifiable by the time she had left the show. This is by design and using it as a complaint shows a fundamental misunderstanding of what Moffat was going for. There is literally a scene in the opening of Hell Bent where some American guy mentions Clara to the Doctor, and the Doctor goes ‘Clara Who?’, which leads into the sting and the titles. He had reached the point where he was parodying it himself because he’d already presented this idea in about 10000 different ways, all played seriously. Clara’s arc is about becoming the Doctor. She dies copying the Doctor’s strategy in beating the villain from Mummy on the Orient Express to save a single person who she thought deserved to live, then selflessly sacrificed herself out of responsibility, and died with her arms outstretched like the Doctor when he regenerates. Clara, after realising how many of his own morals the Doctor broke in Hell Bent to further a toxic relationship, decides to force him and her apart because they’ve become so similar it’s dangerous and harming their own lives. Clara then fulfils an indefinite life of getting to be a time traveller with built in plot armour with her own companion, and still gets to die sacrificing herself because she’s become a spacetime event, like the Doctor. A companion has never become that advanced before, it’s a new idea presented very intelligently in my opinion. The general opinion on Clara has also definitely gone up in the last few years.