Do developers need to join Google,Facebook (FAANG) to be considered successful?

Obviously this depends on your definition of success. If you define it as "Have a job that pays a lot" then clearly there are loads of other companies that pay well, so you don't need to join a FAANG to have that. Likewise for building big things that lots of people use. Lots of companies do that. If you define success as having a notable impact on the work you do then I'd contend that you're less likely to be successful by joining a FAANG - you might be a brilliant cog in the huge machine, but no one is going to notice your output simply because you're surrounded by similarly accomplished people.

Further to that, some people will actually believe you're a worse person morally for joining a surveillance capitalism business. That could well damage your chances of success in other aspects of life like finding a partner or making friends.

tl;dr No, and you might actually be harming your chances of success by joining one.

What a bleak question to even ask. Let's just entertain it for a second to see how long it takes us to dismantle as ridiculous.

If you are a lead developer for Tesla's self driving capabilities, are you generally considered successful? If you are a lead R&D developer for a biotech company that develops the Covid vaccine, are you generally considered successful? If you are a lead developer than built a video game we know and love, are you generally considered successful?

We don't even need to continue, proof by example lays this to rest with a modicum of thought. I hope people realize that "just asking questions" still lofts narratives into the digital ether.