Eurasian blue tits like eating young buds, various insects, and used to go for the cream on milk when foil-topped bottled on the doorstep were still a thing.

Apparently they can take three weeks to build their nest, using moss and spider silk for structure, lichen on the outside, and between 1500-2000 feathers on the inside. No wonder it takes them so long.

I don't remember if I was aware or placed much import on the depth of field benefits from the bigger sensor, but of course shots like those tits would be less impressive without it.

On the other hand, for well-exposed landscape shots the sensor is less significant.

I do think in your position I probably would wait a year or two for the next generation before upgrading, (unless you're specifically hitting the boundaries that the A7iii definitely overcomes).