I have a kid who doesn't eat a big variety of things, so I'm often cooking just for me too. I love cooking and I'm confident doing it, but even I've been in that vicious cycle and I completely get it. Also worth doing a bit of planning, not meal planning as such, because I find that depressing, but having a bunch of things that go together.
So, to go with your salady bits, I'd also throw in the trolley a block of feta cheese, some halloumi, hummus, yoghurt, maybe falafel, and some olives. Plus pitta or flatbreads. Then you've got greek salad ready to go. Wraps or pitta with halloumi, hummus and salad, or falafel, hummus and salad. You can make tzatziki easily with yoghurt, cucumber, mint and garlic (grate cucumber, squeeze out the water, mix with a little grated garlic, yoghurt, mint and salt and a tiny bit of sugar). Then you have several Mediterranean meals and not much prep or decision making to do.
You can marinade a block of feta in olive oil, lemon, thyme, olives and pepper (and a bit of chilli if you like), then tumble over some chopped tomato or cherry tomato for a feta salad.
Microwave bags of rice are admittedly an expensive way of having rice, but they taste ok, and aren't too bad when it's just for you. Makes what to have with the main nice and easy.
A few herbs make a difference too. Add leafy ones to salad and stalky ones to roasting meat, for easy, easy taste, but low effort.
Jars of antipasti veg are good to have with things. Red peppers, articokes, aubergines, semi-dried tomatoes, that sort of thing. You can have them in salads, or with roasted chicken thighs, or put them in salmon parcels too. Or stuff them into pitta or toasted sandwiches with cheese of your choice. And they keep for a while in the fridge, so don't have to eat all at once.
Hope that helps too. I so know the feeling of nice food feeling like too much work. x