What are the disadvantages of ERC20 tokens?

Ah, ERC20 tokens, indeed a cornerstone in the cryptocurrency ecosystem. But let's delve into the flipside and ask: what are the disadvantages of ERC20 tokens? Well, for starters, ERC20 tokens lack a built-in mechanism for transaction notifications. This can be problematic, especially when tokens are mistakenly sent to a contract address. Once that happens, retrieving those tokens can be a Herculean task, sometimes even impossible. This has led to the locking of numerous ERC20 tokens, a situation that can be quite frustrating for token holders. Moreover, ERC20 tokens are limited in terms of carrying additional information during transactions. This can be a hindrance in scenarios where more contextual data is needed, such as when using tokens to purchase goods or services. The lack of such information can increase offline communication costs and complexity. Furthermore, while ERC20 has become a widely adopted standard, it's not without its competitors. Other token standards, like ERC777 or ERC1155, offer additional features and functionalities that ERC20 lacks. This competition can pose challenges for ERC20 tokens in terms of staying relevant and competitive in the evolving cryptocurrency landscape. So, while ERC20 tokens have their strengths and have been instrumental in the growth of the crypto ecosystem, they do have some notable disadvantages that one should be aware of.