I have also had to restyle myself in mid-life due to putting on weight/changing body, and it was hard.
My top tips are: individually all the parts of your outfit and your style sound ok, but it's the combination that is not suiting you or making you look older. If you had a sharp grey bob, but paired it with the jeans/white t-shirt/slouchy blazer comb and nice trainers (of course you can wear trainers, get a nice beige or white pair that you like), then this will give a whole different vibe than if you have a grey bob but pair it with a floral polyester top...(which is kind of what you seem to have done).
Things to think about are- what about new glasses that are very stylish? I can't get these as my eyes are so bad I can't get big fashionable ones, but you may be able to do this. I'd also keep the grey hair if you love the colour (or dye it if you don't) but make sure the bob is sharp and trendy, not just hanging down at an in between length. I also think that cotton, linen, leather and suede look great, compared with polyester and nylon. I know these days they are hard to get fairly cheaply, but try Vinted. A smock in a cool linen colour would have been fine, a polyester one isn't so stylish. Similarly, a cotton safari-type dress would look amazing on you, given your height, but a polyester midi-dress, not so much.
Footwear is also an easy way to update your look. You don't have to go DMs if it's not for you but chunkier footwear/boots in winter, and great trainers in summer are an easy way to update your look, I like the neutral colour ones (beige, brown, cream, pink) instead of white as I'm bored with white. You can wear them, you just choose not to, which is fine, but nothing is preventing you trying these looks. If not, loafers, again in pale colours like tan look really stylish,
Also, I can't believe a cotton or linen blazer with a cami underneath is hotter than a polyester blouse. I do occasionally wear polyester, but I do wear lots of denim, linen, cotton, suede shoes and so on.
With your height and given you are in proportion, a lot of new looks would suit you, such as white linen trousers, straight denim skirts, safari dresses with a belt, you could also wear cropped trousers in navy or black with a cotton blazer and t-shirt and loafers. I would not wear midi-dresses at all unless you are very sure you can style them well, as if they are with other not-stylish things, the whole look just doesn't go well for the middle-aged (IMO).
Hope that helps!