The feedback from the blockchain system that a transaction was included in a block can take from 5 sec. to 10 min. in the case of Bitcoin. Additionally for Proof-of-Work blockchains, like Bitcoin and Ethereum you have to wait, 60 min. and 6 min. respectively, until you can be certain that the transaction is finalized and won't be put back into the pool of unprocessed transactions.
As user we want to have instantly finalized money and data flows, but this causes a lot of problems when building a great DApp on top of current systems. Basically you have to fake it for the user and if something goes wrong with the processing, it has to be mitigated by the DApp - e.g. through a fraud prevention system.
Mining pools, Layer-2 aggregators and Validators in regular Byzantine Fault Tolerant (BFT) consensus algorithms are all in positions to censor transactions and act in their self-interest by influencing the transactions added to a block.
Financial arbitration is important, but in a system with infinite arbitration possibilities like Ethereum, they also help to drive up the gas cost and render the system unusable for a broad set of, more cost sensitive, IoT driven applications.
The use of a competitive consensus algorithm in the form of Proof-of-Work, causes a very high energy consumption for Bitcoin and Ethereum. The value function of these systems also lead to higher and higher energy consumption over time and worsens the already very poor energy efficiency per transaction even more.
While it is important to have a well functioning DeFi ecosystem, it also has slowed down the preparations to integrate a broader application space. So far there are no holistically designed blockchain systems with an integrated decentralized identity (DID) system for organizations and IoT devices in connection with a native support for decentralized data storage like Swarm.
This will be needed for any real world application in order to fulfill the needs of authorization, identification and simple data integration for payments. Data marketplaces as we can see with Ocean v3 or the UPort development for DID's are a first steps into the right direction, but it needs to be integrated into an affordable system to leverage on composability.
The low scalability of Ethereum in combination with the great composability for DeFi, leads to transaction fees only justifiable for high value financial transactions.
When on-boarding new users it is very hard to explain that there is a need for a native coin, which is needed to pay for transaction fees and that creates massive UX frictions.