Let's just say she did okay today.
Serena's not really played for many months, and of course she's extremely rusty and that's not helpful to a soon to be 40 year old. She is still very inconsistent due to the rust and the only way to stop her inconsistency is to play more, but nearing 40, that's a difficult balance. It takes her a time to get ready on court, and she has a long ways to go before she even gets most of the rust off.
As for Venus, I feel that she should play as long as she wants to. It's her right. But I know we've seen the last of the 2017 Venus who came close to winning a singles grand slam at the US Open. With Sjogrens, and naturally slowing down in movement due to back/knee issues on and off the last 2 years.
Serena is a rare tennis player (I feel the GOAT) who can make it into deeper rounds at her age, ranked in the top 10 (#8 I think) even though with she has little match play, match prep and is rusty as all hell.