There are at least three different reasons this is bad.
First, this is one more sign (of about 15 court cases at this point) that this court is willing to give Trump massive powers simply because he is pushing for them and they agree with him politically. And there's no reason to remotely think he's going to stop.
Second, it means that the Presidency (already an already too powerful office in the modern form for any one person) is going to be even more powerful under for the first time under a far more authoritarian person without any safeguards in place.
Third, is more subtle: even if we get through this with Trump with only some damage, the long-term damage and threat to stability is massive. In general, parliamentary systems or presidential systems with somewhat weak presidencies are more stable than those with powerful presidencies. One sees this in for example the high instability in many presidential republics in Central America and South America. The standard explanation for this is that when there's functionally a winner-take-all system, the stakes becoming higher and the degree to which any side has an incentive to moderate becomes small. One question then is why this hasn't happened in the US? One explanation is that the US had the illusion of a not deeply strong President, in part because everyone (including the Presidents) agreed tacitly not to push the limits of their authority that much. The precedent breaking nature here undermines that illusion, and makes it more likely that we'll have years (possibly decades) where the Democrats and Republicans will even more than usual treat everything as a zero sum game with no respects for democratic norms.
The bottom line is that everything about this is bad.
The masks were stupid. Everyone lifted them up to do business in public, everyone was breathing out their car windows in traffic while people drive in long straight lines breathing each others air from non-airtight vehicles.
This is confused at multiple levels, but does almost touch on a valid point. It is true that a lot of people were awful maskers, and lifted up their masks all the time, or had terrible seals, making their masks not function. And then you had people doing things like wearing masks in indoor restaurants and then taking them off when they sat down to eat as if their dining table was somehow protected. And if you go back to Slashdot, you'll see me explicitly saying that all of this was awful behavior. People failing to mask properly isn't a problem with masks though any more than people dying in car accidents due to not wearing their seatbelts is a sign that seatbelts don't work. And the point about car windows out non-airtight cars misses something we figured out pretty early in the pandemic, namely that outdoor environments in general were pretty safe.
People became immune to covid without needing a hundred vaccines. No masks now and everyone is okay arent they.
People didn't need a hundred vaccines, but we're still getting new covid variants, and vaccines are still helping prevent people from getting seriously sick. Vaccines worked, and they drastically saved lives. Here is a really good essay about that https://www.natesilver.net/p/the-2-key-facts-about-us-covid-policy which shows how prior to the vaccines, death rates in the US among Democrats and Republicans looked nearly identical and only after vaccines showed up they started diverging. There's one easy explanation for that. And it is worth noting that the author there Nate Silver, generally takes the position (and argues explicitly in that piece) that mask mandates were not substantially effective, even as vaccines worked really well. It may be worth realizing that while you somehow see vaccines and masks as interconnected issues, they aren't, and not everyone falls into the vaccines-bad-masks-bad and vaccines-good-masks-good categories. To use two fun anecdotes: One of the most strict maskers I know was a couple who were highly anti-vax and was also taking HCQ as a preventative. One of the most vocally pro-vax people I know is a Rabbi who despised not getting to see his congregant's faces and was pushing for the vaccines so people would feel comfortable unmasking. Maybe don't treat all matters as some giant soccer game with two large sizes?
If a thing's worth doing, it is worth doing badly. -- G.K. Chesterton