in theory, there is nothing wrong with spacers, as long as the spacer itself isnt bad enough quality that its gonna fail.
the only thing a spacer does is introduce another mechanical connection, it DOES NOT create any extra strain on the standard hub/studs.
people mainly think spacers cause more strain on the standard hub because it creates more leverage, 2 points about this, 1: putting a spacer in there has no more effect on the standard hub then going a lower offset wheel (for instance putting a 25mm spacer on a +30 offset wheel is the same as going a +5 offset wheel). 2: if anything, ur reducing leverage in most cases as ur bringing the offset closer to 0 neutral (middle of the rim)
a spacer is effectively the same as offset, the only difference is instead of the extra metal on the mounting surface being casted on when the wheel was created, it is being connected there with a mechanical connection.
now as long as this mechanical connection is created with qaulity parts, there is no issue with this, when u put on new spacers, they are usually a lot less likely to fail than ur old worn standard items, so ultimately the weak link is usually in the standard existing mechanical connection, not the new one that u introduce.
but in the end, u are introducing another mechanical connection, which is A weak point that can fail, but usually not the weakest point.
now, all this is relying on the fact that everything is kept hubcentric, one of the biggest issues with spacers is people dont buy hubcentric spacers or they dont use hubcentric rings, now a lot of people dont use the hubcentric rings with their aftermarket wheels anyway, but when ur using spacers as well and u have 2 mechanical connections, ur doubling the issue. basically studs are only designed to take longitudinal force, when u dont keep things hubcentric (hub ring on mounting surface completely filling the centre hole in the rim, keeping it snug), the wheel is allowed to move sideways on the mounting surface, this introduces sheer force to the studs, which the studs are not designed for and have bugger all tolerance for, so they can fail.
the last point is make sure u loctite the nuts on the inside, not that there is a big chance they will loosen, its just if they do u wont know as u cant access them.