I'll guess the following, as someone who generally appreciates cryptocurrency:

1. People who speculatively hold an asset have an incentive to talk it up, even misrepresenting their own beliefs about its merits and future value. Thorstein Veblen wrote a whole thing about how this happened with real estate in the U.S., where people felt immense social pressure to persuade the broader public that a particular town was great because their assets and their friends' assets were tied up in land in that town and they all wanted their property values to rise. It's annoying for people if they feel that they're getting a pitch that's ultimately inspired more by someone's (possibly undisclosed) market position than by someone's honest assessment of the situation.

2. Altcoin creators and early investors stand to become rich, possibly at other people's expense, if there is sufficient interest and enthusiasm for an altcoin, even briefly, regardless of the altcoin's level of technical or economic innovation.

3. There's a lot of disagreement about economic ideology and policy issues around cryptocurrencies, familiar examples including Bitcoin's intentionally deflationary monetary policy and Monero and Zcash's privacy. This can add an extra level of contention and disagreement in this area, sometimes in the background, and people may be upset by the particular choices or policy goals that others have adopted. (And a lot of people have diametrically opposed beliefs about whether governments should have more or less power than they do today to set monetary policy, to monitor transactions, and to prevent particular entities from receiving payments.)

4. We've seen with the DAO and the current Bitcoin forks that there's also uncertainty about governance, including a conflict between people who want to see purely code-based rules set at the outset and enforced forever, and people who want some kind of community to have a way to amend the rules. To some people, the failure of meta-consensus about governance and decisionmaking is a long-term fatal flaw in cryptocurrency communities, and a way of glossing over something really necessary.

5. Cryptocurrencies have experienced high rates of frauds, scams, and theft that suggest to some people that they can't be taken seriously as a real part of the financial system, since the risks seem unacceptably high and there aren't straightforward ways to insure against them. Most new projects don't directly change this situation.

6. We've also seen tons of projects adopting blockchains that obviously don't need them because the participants in the system already trust each other or at least already trust a common authority that they agree is allowed to adjudicate disputes. In that case, the common authority can maintain a central database, or the participants can maintain a simpler distributed database and appeal to the authority to resolve any disagreements. (Maybe there are some cases where something blockchain-like is ultimately cheaper because it simply reduces the frequency of disputes that need to be adjudicated, but in any case a lot of people adopting blockchains seem to miss the point about trust and decentralization.) So there is a skepticism that says that most often when someone used a blockchain it was probably for buzzword-compliance.