Over the last 10 years I have lived with 7 systems in different flats and houses. Where we have had an old combi, I can sympathise with the OP. Running low levels of lukewarm water, and then having the pressure drop is very annoying.

Even more annoying is when the bloody hot water runs out on a cold Monday morning in flats where you have had a tank and female housemates getting up before you, or when you really need a soak in the bath. Perhaps modern tank systems have fixed this, I don't know.

The best compromise has been a new modern combi for me (live with up to 4 people and 2 bathrooms). They have always been fine with a bath and a shower, in my experience, running plenty of very hot water.

The parents had a new combi installed a few years back and they are very happy with it (solves the issues of the last one and warms the house much quicker as well).