My concern is the potential for the combination of Denuvo and microtransactions to be used to interfere with game experiences, in future. Denuvo has been very successful at slowing down piracy, but, as they themselves point out, it's not actually DRM - it's an anti-tamper system for the game executable. It works to stop the circumvention of other DRM systems, but it can be used to lock down the game experience in other ways, too.
The problem with this, is that it can also stop us tinkering with our games as we wish to. It would, for example, prevent many of the low-level mods and important fixes that have transformed the Bethesda games - no more memory fixes or ENBs.
If publishers can construct games in such a way as to encourage us to make microtransactions, there's a temptation to start messing with the gameplay to increase our incentive. Not only that, but if they can monetize and lock down cheats, like adding in-game money and XP, they will prevent us from making those tweaks ourselves. Many times I've made tweaks to games - disabling stamina drain when running, adding back money, XP and items after a corrupted save, editing character stats to change my build, an so on. I'd have probably shelved those games if couldn't have done those things.
I could go on, but I'm sure you get the point.
I accept what people are saying about the microtransactions being a non-issue to the enjoyment of this particular game, but I think it would be no bad thing if the publishers get the message that their customers don't appreciate them heading in that direction.
I don't give much credence to the claim that Denuvo is responsible for performance issues in DX:MD. Why would a DRM cause such supposed issues only in some games but not in others?
I doubt that Denuvo is causing general performance problems, but in theory it's possible. Essentially, when they code the game, they call certain processes to run through the Denuvo VM. This will massively slow that process down, so, unless you're crazy, you only run those things through Denuvo that are not performance sensitive - things like loading screens, menus, background calculations, etc. It would be possible to kill the performance of a game using Denuvo, but only if it's implemented incompetently.