In fact, when you say "adoption" here, what you are actually talking about is investor adoption.
There are challenges in the scaling issue, yes, but there are also solutions. Lightning is struggling a bit with adoption currently, but there is finally some movement with sidechains (ZK rollups etc.) and other L2 solutions, where slowly more decentralized concepts appear. As on Ethereum there is already more variety, and the concept seems viable and popular, I don't see why this shouldn't be achievable with Bitcoin too.
If you were right this would actually be a quite pessimistic stance. As an "investment" vehicle alone, Bitcoin would not have any real value. Bitcoin has USPs like censorship resistance and worldwide availability. While these characteristics can also appeal to "investors", if they "invest" using their own wallet, investing in a Bitcoin ETF or "exchange bitcoin" does actually not make use of them.
IMO you're seeing the crypto world a bit black and white. Some of your forum contributions are interesting and valid but others are not.
(And if you want to direct the focus to altcoins: all cryptocurrencies face the same challenge between node decentralization and on-chain throughput. If there was any breakthrough there, Bitcoin could adopt it.)