Perhaps what is meant by "don't work" relates more to the value/price/volatility vs actual transaction functionality.
What you describe above has to be weighed against loss of value for holding until accumulating enough to trade for $ no, as well as general fees associated with trading for $ generally?
Else what really is the point, if maintaining the value transferred isn't possible?
Stellar also supports the creation of stablecoins [1], which tend to have a consistent price relative to some other asset (Often USD).
The way stellar works is pretty smart, if I have some currency on the stellar network and you only accept some other currency, it automatically looks for people willing to exchange them to find you a good rate. So even if few people use your favorite stablecoin you can still accept payments in it.
[1]: https://cointelegraph.com/news/ibm-backs-new-us-dollar-pegge...
My personal favorite example is:
https://www.stellar.org/papers/stellar-consensus-protocol.pd...
Transactions take a few seconds, 10000 transactions per $.01 as well as no mining for coins so it is not a bad coin for climate change compared to say Bitcoin and the mining farms.
Just my $0.02