Thank you for posting your thoughts!

When something gets your attention and you get a sense of caution, then caution is probably justified.
This must not stop action taking or decision making if you are planning a website. If it does, it will never happen. Concern should lead you to research until you have confidence in understanding the matter at hand.

You cannot avoid risk. Not ever. Just put risk into context. Consider input from others but don't rely on anyone to choose for you because you are capable and will only get better at it.
The vulnerabilities of blockchain, as I understand them, have primarily involved money on exchanges but if a costly (expensive to perform) attack on blockchain were to happen, the goal is to double spend digital currency, or move it between wallets (not on blockchain necessarily- but through exchanges) not to steal data. I'm not an expert but am putting limited knowledge into context. Data can be stolen much more easily and without the high cost of massive computing power needed to gain control over a blockchain. So probability, in my mind is much higher - that my website files and data- customer data are at far more risk on centralized hosting drives.

Anything could happen anywhere at anytime to anyone but mindful consideration of hype free information, using it to side with probability plus a bit of intuition (after fear is addressed, thanked and allowed to go home), should make most choices worthwhile.