A 30 year old should be investing 70% of his net worth (100-age rule). Holding too much fiat is definitely "wrong", even by conventional investing norms.

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For years, a commonly cited rule of thumb has helped simplify asset allocation. It states that individuals should hold a percentage of stocks equal to 100 minus their age. So, for a typical 60-year-old, 40% of the portfolio should be equities. The rest would comprise of high-grade bonds, government debt, and other relatively safe assets.

https://www.investopedia.com/articles/investing/062714/100-minus-your-age-outdated.asp

The (100-age)% is traditionally in equities (stocks), but crypto has a role too in this modern age.

Holding too much fiat is definitely not good, even by conventional investing knowledge!

According to the same article, "However, at a time when adults are living longer and getting fewer rewards from “safe” investments, it might be time to adjust the “100 minus your age” guideline and take more risk with retirement funds.".

It seems "safe" investments are no longer yielding enough for retirement. There is definitely a place for volatile assets like cryptocurrency in one's retirement portfolio. As the saying goes, high risk high reward!