I think it is hard to argue against your conclusion in the OP. Buy and hold SPY really is guaranteed victory...and with interest rates so low it seems like a great place to park cash for the long term.
as for shorting vol...that has to be about the most unappealing strategy to me. the literal definition of picking up pennies in front of a steamroller where you look like a genius 99% of the time only to blow up when it gaps like crazy.
UVXY went over 12x in less than a month in 2020...
Would need some serious discipline in cutting losing positions...Imagine waking up and opening your trading platform to see that you are down 200%+ overnight on a short UVXY position with no end in sight. Trying to tell yourself "it'll come back down soon" can easily lead to a margin call then liquidated position forcing you into a cardboard palace under a highway overpass on southside.
Puts would at least put a cap on losses at 100%...however i cannot say that long puts are a viable strategy either. a quick glance at the options chain looking at historical value of puts of various dates having high volume strikes show a loss most of the time (typical time decay and IV crush).
just brainstorming here but maybe a long call short common strategy would work well...would reduce your overall return but could sleep better at night having insurance. sucks that VIX and UVXY have sort of a reverse skew where call options are more expensive than puts. Makes sense because they essentially inverse the S&P...just sucks.