I wouldn't say 'love is lust', but it's fair to propose that a great many people get swept away by the rush of oxytocin and other hormones that flood the brain in the early stages of a relationship, then aren't able to adapt [or find they're incompatible], once that initial wave subsides. That wave isn't what many people would call
real love, which is rooted in more stable emotional and cognitive ground and not as affected by surges of chemistry.
A friend of mine introduced me to the
Four Greek Loves [what augiedogie missed was
Storge, which he or she seems to have consolidated with
Agape], and also an interesting taxonomy of
love styles as devised by Psychologist John Alan Lee. Love takes many forms. It's part of what makes it so captivating to the imagination.