but I’m pretty sure customers don’t actually want the same game and content for forever.
The success of long lasting MMOs like WoW, EVE, FFXIV, GW2, Warframe seems to suggest otherwise, as well does the longevity of games like Fortnite, LOL and other non-MMO gaas games. There are even other examples that I'd count - I'd call paradox games like stellaris GaaS as well since they live off constant updates (stellaris has had them for 7 years now and going) and paid DLC. Hell, there's people that have been playing Ark, Rust and games like that for a decade now.
So I'd say there is definitely an audience for it, a massive one, as long as its done well. Destiny devs just sucked at it and had years of controversies, this is just the latest of their fumbles.