In the end there's no Marshall, Newey, Wheatley, Fallows (insert other big names I might have missed) that are left in the team. The team is what it is today and it's on them to keep doing a good enough job.
And also, just my 2 cents on Newey and other engineers -- F1 of today can't be done by just one person or just four or five people. It's a massive team effort. Sometimes things work, sometimes things don't (and this is true for every team) but usually with good leadership, you figure out when things fail quickly enough and come back. In fact, Red Bull did this very very well in 2020, going into 2021. Right now that bit is missing and that's worrying.
The RB18 also had correlation issues -- recall Brazil for instance although you can chalk to out a sprint weekend. The RB19 also had the issue at Singapore. The RB20 had big issues and the RB21 is following the same path as the 20.
Correlation issues with ground effect cars are always going to be there -- the key as it seems is to get a model that is as close to the real world. Looks like we have diverged from there.