SCALABILITY ISSUES: some network like Ethrerum and bitcoin can become slow and expensive during high demand.
For ethereum I would understand that it network trx fees are fairly high but not for bitcoin except for when there a network congestion leading to the mempool been overwhelmed, and occurrence that seldom happens. Of which it shouldn't be a valuable reason to risk opting for altcoins.
USABILITY: we the newbies find it so difficult to understand and manage cryptocurrency safely.
We all know that regulations does affects the usability of bitcoin in any society. Government policies has always dictated to a large extend how much people and institutions are willing to use bitcoin as legal tender or means if transaction within a society. So it's not a thing of about being a newbie or oldies.