What are the downsides of granting blanket pardons of the sort Biden is considering?

Isaac Chotiner asks lawprof Rachel Barkow, in "Are Blanket Pardons for Officials on Donald Trump’s Target List a Good Idea?/As the Biden Administration considers granting clemency to officials singled out by Trump, a legal scholar explains the advantages and pitfalls of extending such protections" (The New Yorker).

Barkow responds:

One is just making sure you actually have a comprehensive list, because, if you’re going to single out certain people for protection and you miss others, then the people you miss are going to be the ones that the incoming Administration is going to target. Let’s say the current Administration pardons twenty or thirty people. It’s not as if there aren’t others who also worked on congressional investigations into Trump, or were part of January 6th prosecutions, or were members of the Mueller team—whoever it is that’s on the Trump hit list. If you are not comprehensive in terms of the list of people that you’re shielding, then I suspect what the incoming Administration is going to do is just go down the line and find whoever’s left, and prosecute them. Because doing that still enables it to do what it aims to do, which is to embarrass people, and make it into a political sideshow. It turns out that you’re not going to get the benefit of avoiding all of these really awful investigations.Then, the other issue is the fact that it might be better to have a public investigation of some of these ridiculous claims so that people can see there’s nothing to them, and can learn how the government actually works, and can realize there’s nothing there. There are some benefits to having investigations when someone’s name is cleared, whereas, if you do a preëmptive blanket pardon, there’s always that question of why they needed it. Was there something that actually was bad that was going to come out? If you keep things open and transparent, you avoid any kind of taint or doubt that someone actually was engaging in something problematic.

That last sentence sounds way too optimistic, because things will never be perfectly open and transparent, and it's hard to see how to avoid any kind of taint or doubt, but Barkow's point is that the blanket pardons will make things seem closed and opaque and will create some degree of taint and doubt. And, as she says, there could still be all of these really awful investigations. You can't even get opacity even if that is what you want.

Not discussed in the interview, but something I'm thinking about is whether Trump will benefit from these proposed blanket pardons. He may end up hurting his own cause weaponizing the government the way it was weaponized against him. If the pardons stop him from doing that, he can excoriate Biden for pardoning those who persecuted him and he will never need to prove that what they did violated any law. Yes, he could, as Barkow says, find targets who were not recipients of a pardon and pursue investigations against them, but he would also have the alternative of saying Biden covered it all up, in which case he can persist in making whatever claims he likes.

Perhaps Biden should stand back and let Trump make more mistakes.