My dad used to tell me that they can cause premature axle bearing wear.
I hope they're safe, I just installed Eibach 25mm spacers on all four wheels on my new 2021 RT I did it so I could use a set of aftermarket wheels from my '17 GT. Stock wheels are are 24mm offset and my FK Ethos wheels are 35mm. By installing the spacers I'm, in effect, changing the offset of my aftermarkets to 10 mm. That would mean I've only moved the set-up out 14mm (a little over 1/2 inch. The Eibach spacers are are a quality product. My wheels & tires look great with the slightly more aggressive stance and I see no problems with what I did.
As a side note....if anybody wants a brand new set of factory wheels and Goodyear Eagle RS-A's.........check out the For Sale forum!