You really think so? I would argue that Picard and Data (or more precisely, the actors who played them) were the only things that made the show work. Get rid of them, and TNG would have been a hollow shell of itself. (Riker in particular I always found to be an intolerably annoying character. But then every Trek series after TOS seems to have at least one of those...)
Yes, I think so. Picard and Data were the very obvious fan favourites, of course. Much like Spock was on the original series. But like Phase II could have had existed without Spock and a replacement instead, TNG could have had existed without them. Cmdr. Shelby was even introduced as Rikers "Nr. 1", to replace the Picard-Riker relationship.
Of course the show would have massively suffered for it - Picard was one of the biggest strengths of the show, and replacing him could have proven very difficult, and probably audience figures would have dropped. It would be like on Stargate SG-1 after Richard Dean Anderson left. It'd be harmful to the show. But the show could have survived that. OTOH a show called "Buck Rogers in the 25th century" coudln't survive the actor playing Buck rogers leaving. Or Adam West leaving Batman '66, or Tom Sellek leaving Magnum, Veronica Mars leaving... Veronica Mars.
Those shows have a clear main character they are completely centered around. Star Trek always was more an ensemble piece - with the Captains and the fan favourite characters taking center stage, but the show not being entirely dependant upon them. DS9 and DIS are somewhere in the middle between these two extremes - they have a more clear "main" character. DS9 is especially interesting, as Sisko's screen-time share isn't that big compared to all the others on the show, it's just the role he plays for the various storylines - every aspect of the show is centered around him as the main presence: The station he commands, his family, his role as a spiritual leader of an alien species. Take him away, and ALL those storylines suffer. The "space station" storyline could survive - DS9 simply get's a new Captain - but the "Sisko's family"-storylines and the religious Emissary-storylines (which are also central to the show) would crash down burning.