You don't need to mix up your staples, you need to mix up your choices and extras.
The staples, for me, are onions, carrots, celery, potatoes. These keep well, so you don't need to worry that you'll buy them and never use them. (I don't always have spring onions, red onions, shallots, but they add regular variety.)
I always have garlic, ginger, chillies to add flavour.
Then add more variety by choosing different kinds of peppers, tomatoes and mushrooms - not just the same old, same old every week.
And rotate different leafy vegetables (cabbage, kale, spinach), brassicas (caulis and broccoli), different types of mushroom, different salad leaves, sweetcorn, asparagus - and more, to me, exotic vegetables: plantain, bean shoots, okra etc.
I'm not sure the typical Britsh concept of of "salad" is really helpful here if it brings to mind what my granny used to serve: lettuce, tomatoes, cucumber, boiled egg.
But: "A salad is a dish consisting of mixed, mostly natural ingredients. They are typically served chilled or at room temperature, though some can be served warm." So that's basically any combination of vegetables.
Hugh Fearley Whittingstall's veg books are great. Lots of ideas to put vegetables more centrally in your diet.