I agree with selling them both... but buying a burnout walking Messi? Fuck no.
Regarding the selling part, I would absolutely sell Lautaro while he still has *some* perceived value. It's a much better option than having him as a rotational striker. At this point it's clear that he won't develop the finishing instinct and he is simply not good enough. Tough luck, but it is what it is.
Lukaku is a lot trickier. If some major club comes flaunting around at least 90m I would take it and run. There are 3 or 4 of those clubs in the world so the chance is low but if it happens.. we better go for it.
I wouldn't mind him staying under the condition that our manager is someone who realizes that he isn't a big match player and that he should not start big matches. Simple as.
I don't give a fuck about statistics, about goals scored. You can statpad Spezias and Torinos all you want but what good are you if you aren't coming through in big matches. Not once, not twice, but routinely not coming through in big matches.