We have less pressure here than in UK, but still significant. We are online grocery shoppers for many years also. DH and I both still working FT from home and managing DD's needs (school, exercise etc - important as she is ASD/ADHD). I am on the vulnerable list due to asthma requiring steroid inhaler daily.
So I have felt somewhat guilty but continued to organise myself ahead of time with grocery slots. We were prepped ahead of time for many items but not all, and we need fresh too.
I have managed to get a slot every week up to early May. It requires being organised and planning ahead. But I have also been lucky enough that, on Easter week when there was huge extra pressure and a lot of community helpers doing shopping for more vulnerable people, we had enough to get us through the Easter weekend (even if not with a nice roast/chocolate eggs/hot cross buns etc), and leave shopping until 1 of us could go in person midweek last week, so I gave up my slot that weekend as it wasn't vital.
In fact, most weeks, the shopping has come between 1 and 3 hours early, so while I know they are adding in deliveries that come by phone and email rather than the online system (from hearing the managers while I've been instore 1 week for extra milk), but seem to be managing ok.
I'm trying to use my slots sensibly, getting plenty of fresh stuff, topping up store cupboard items we have used, and also being flexible as many things are not coming having gone out of stock between ordering and delivery. I am also offering to add items for others on our street - we are doing a shared bread order to the local bakery once a week for example, and for my retired DAunt living alone nearby.