I've been mulling this overnight and something else came to me. The airlines don't really guarantee anything about their flights. Not timing, where you'll sit (even if you preselect a seat) and, in this context, what aircraft you'll fly on.
In the current circumstances the little viewing I've done of airline websites to make bookings suggests to me they are still publishing schedules for anything from about 3 months from whatever day you are looking on based on their historical data. What they then do is take a more realistic view of what they think might happen and they then change the assigned aircraft to meet the actual booking levels. What that means is that, if things continue as they are you could book a 777 (despite your misgivings) and end up on something completely different. If things get better you might have booked a 787 and end up on a 777.
Even back when things were stable I've had it happen to me. I booked a 747, checked in online the night before and saw a 747 seat plan, got to the airport and I was given a new boarding pass for what turned out to be a 777.