It’s true that both Superboy and Supergirl along Ultra Boy have usually been part of what makes Legion “Legion” (and there’s Laurel Kent and MORE!).
There’s only one Silver Age Superman Family character missing from this, and now that Monster Boy is a member, I think it’s time that we nominate Krypto for the Legion!
This takes me back, the first time I ever “rage quit” a comic. Nine year old me quit reading Legion of Super Heroes and took his money over to New Adventures of Superboy until he came back. In fact, this stretch of comics was the last one I purchased in the 1990s to finish up my Legion run. They still rank at the bottom of my Pre-Crisis Legion eras.
I still prefer my Legion with Superboy, but I can see why most don’t given their 1980s success without him.