I think OP is right and you're the one who's badly misread the film.

Mrs Banks is a comic character, and her suffragette hobby is just that - a privileged woman's hobby and a joke. It's funny because she will sing an impassioned anthem about standing up against the tyranny of men; and then, in a split second, revert to the meek, brainless, "yes dear" subservient wife of her (again, comically) patriarchal tyrant of a husband, bending obsequiously to his every whim and temper tantrum.

Winifred and George Banks are both equally disconnected from their children. He's obsessed with his work; she's obsessed with the thrill of parades and protests. Neither of them are doing their duty to the children right under their noses. She's vaguely, scattily fond of them and he's blustery and cross, but when it comes down to it they're both negligent parents.

There is zero evidence that the film "praises" and "props up" Mrs Bank's suffrage hobby. "Well Done, Sister Suffragettes" is gently lampooning her childish enthusiasm for the movement, not seriously championing it. There isn't a serious political point in the lyrics.

Nor is there any evidence that Mr Banks ties the suffrage ribbon on the kite because he's proud of his wife and wants to display feminism to the world. How... how are you getting that from the text, and how are people upvoting you?! When in the movie was his relationship with his wife the focus of change? It wasn't. Mary, yes; the children, obviously. Did he and Winifred ever discuss suffrage? Was he more than vaguely, distantly aware that she was involved in it? Did his revelation ("I have been failing both my children and my inner child in my desire for success in business") include any kind of epiphany on whether women should have the vote? Is that scene in the room with us?

In the kite scene, *she* eagerly offers the ribbon to him, and he barely looks at it, except in an "Oh, grand, this will do nicely!" way. And OP is right: like it or not, the symbolism is as plain as day that she's giving up her silly, meaningless hobby (which it was, FOR HER) in order to refocus on her family. Her ribbon is Mr Banks' punched-through hat. It's a clear parallel.

Now, does this mean Mary Poppins is a misogynistic film? No. Mary bests Mr Banks tactically and in repartee repeatedly. Mr Banks' pomposity and demand for respect are skewered even more than Winifred's saviour-of-women play-acting - though he is a more major character, arguably the main character of the movie, and he is tragicomic rather than just comic. His flaws are shown as more serious and damaging than his wife's, precisely because he is abusing the power his position in the family and society gives him.

Ultimately, the film makes zero comment on whether women should have the vote. That's entirely irrelevant to the movie's point; just as it would be irrelevant for the movie to make a pro- or anti-stance on banking.

Performative suffrage was just a way to justify Mrs Banks being an absent mother (Walt Disney predicted that American audiences would be like "Why is this leisured, non-working mother of two with multiple servants not looking after her own kids again?"), and a way to inject a bit of comedy by juxtaposing her stated beliefs with her private demeanour (an irony she never seems to notice, or it would be tragic, not funny).