Wolfman's Titans are not legacy heroes because Cyborg, Raven & Starfire are original characters. Robinson's Starman was successful for the same reason Mr. Terrific is successful, the original hero didn't have a strong enough fanbase for people to care.
Since the death of Barry Allen, DC has designed legacy heroes for the sole purpose of replacing an established hero, but overall it has not been a financially successful endeavor, because it usually results in a fan backlash and plummeting sales.
(Yes Wally West was a success story, but he had already been around for 30 years, so fans accepted him, but they brought Barry back and now you have a partitioned fanbase)
I've flat out quit comics twice, and both times it was because they offed or shoved aside my favourite heroes to replace them with a new legacy hero, to which I gave DC the big middle finger to and stopped buying, I came back, but I've met countless of other fans who have not. They quite reading DC and are never coming back.