Looking at the current downfalls of big companies and tech, can we assume that decentralization is the future?

I wouldn't call going from mad profits to okay profits a sign of downfall. Having decentralized technology doesn't mean decentralization will actually happen. For instance look at E-mail. It is technically a decentralized service, but most people still uses services provided by big tech vs operating their own servers. Such a system does give you more choices, but don't expect this future will be without big tech.