This is not intended to be "FUD" post but rather a "perspective" one. In the traditional FIAT world, money is concentrated in a handful of people due to abuse of power. In the crypto world, and especially in Bitcoin, this happens because of the early adaptation from visionaries and the original believers that adopted the technology.
We still don't know if Satoshi Nakamoto was a financial visionary, a revolutionary, a researcher having fun or a government agency deploying a beta digital currency to replace the old obsolete system. We can speculate and hypothesize about all the scenarios but in the end, we will be left with nothing other than a tinfoil hat.
Either way, the story behind Bitcoin should not distract us from the main point. A few people hold the vast majority of wealth. It doesn't matter if they spread it through a few wallets. We are talking about less than 0,0001% world distribution in wallets and an entire market in the billions depended upon these few individuals. Some coins have not moved for ages even if the price has climbed or plummeted in crazy magnitudes. If one single whale decided to play the market, they could easily spread havoc.
This brings us to the point of decentralisation which was one of the main points of Bitcoin and the thereafter blockchain development. The technology can be decentralised but that does not mean the system is. As of recently,6 mining farms controlled most of the ecosystem. Most new people entering are playing with launch money. It is not clear how and when institutional investors entered the scene. A small bear market on Bitcoin shakes the entirety of all other projects.
I wouldn't call Blockchain a bubble but I would definitely call Bitcoin one. I do not believe a Bitcoin crash will decimate the entire ecosystem as it did in the past. I believe this time will be different. The market cap of Bitcoin will eventually flow into the alt coins. It will be a slow process that will last a year or more. This will happen partially because Bitcoin is an old technology and as much as it wants to act as a store of value, money is dependent on velocity, not hoarding. The second important reason is the blockchain itself. If Blockchain technologies are to take over the world all that money will not just be sitting there waiting for the lambo moment. They will flow in order to grow.