We can, but I don't think we should. We had iterations of nullifying orb that were much more inclusive, and they very quickly became mandatory. This left us with the options of either restricting the Rune to be more situational or remove it. I believe it's important for a number of mages to have a way to plan for a lane where the range disparity against other mages is a defining element of the early game, so I would prefer we don't remove the option outright. When we tested weaker general versions of the rune, it stopped being understandable. Shields that pop in reaction to damage tend to get crushed by the incoming damage, and this is especially true at small values.
That being said, I know physical assassins are a constant source of consternation on these boards, and we have seen that this is even more pronounced since 7.22 dropped. We always expect balance to be a bit rocky after changes this large, and we're definitely knee deep in the chaotic, unoptimized state right now. You're likely to see some small nudges to individual runes or champions for the next patch or two as we let some of the dust settle.
If I could make one small suggestion, there are a number of us watching the boards right now, looking to talk about the state of the game and Runes in general. This can be really hard on gameplay boards because of the exceptionally negative hyperbole that tends to be so prevalent. It doesn't help that dissenting opinions are also frequently downvoted into oblivion (as there are a few examples even in this thread). I personally love to talk to players and do so on a lot of different platforms, but boards is sadly one of the most draining. I figured it might be worth pointing out that we'd really love to talk on here a lot more about Runes, if folks are open to having actual discussions.