The noun criticism can be countable or uncountable. In more general, commonly used, contexts, the plural form will also be criticism. However, in more specific contexts, the plural form can also be criticisms e.g. in reference to various types of criticisms or a collection of criticisms.

Does criticism have plural?

The plural form of criticism; more than one (kind of) criticism.

Is criticism an uncountable noun?

[uncountable] the work or activity of making fair, careful judgements about the good and bad qualities of somebody/something, especially books, music, etc. She has written several works of literary criticism.