Slavery may have been 'acceptable' at one time in the sense that it was legally permitted, but it was widely opposed and deplored as well. Many thinking people even then understood it was evil; that is how it got to be abolished in the first place.
I don't think regular people today have anything to be reproached for. A very few families at the time accumulated vast riches through the slave trade, but most people emphatically did not; we can acknowledge that slavery is a whole different order of evil and still accept that most people in the UK at the time were badly exploited and impoverished too. So why should their descendants feel any guilt for this?
I don't agree though with the angle 'let's demand reparations from the French for 1066'. This is really very recent past: after slavery was abolished it was agreed to pay vast amounts of compensation; none to the former slaves, all of it to the slave owners for the loss of their human 'property'.
Do you know when that debt was paid off? 2015. That means that generations of taxpayers had to pay off that debt - also that descendants of slaves who worked in the UK up to 2015 actually contributed to clearing the debt that was created because of a payment made to their ancestors' owners, just so that they could be freed.
So it would be nice if the other families who have built (and today still benefit from) huge wealth historically acquired on the back of slavery could find a conscience and look at ways of making reparations. It would be nice if our beloved Royal Family (who are heavily implicated) could set an example of leadership in this regard. And I think as a nation we should stop worshipping wealth, accept the ugly side of our past and look it in the face. But collective individual guilt? I don't think so.
Anyone who deplores slavery and human exploitation needs to take action against it here and now. That means things like: don't buy cheap fast fashion. Don't access porn. Report any potential slavery or exploitation if you encounter it.