You don't understand the context of the manifesto.

It isn't the method to achieve communism, it's what the party he wrote the manifesto for should do if they gain power.

Imediate policy isn't the same as end goal.

You should read the whole manifesto and not what biased people have to say about it.

Edit

Read the book.

Stop thinking what other people tell you to think.
https://www.marxists.org/archive/marx/works/1848/communist-manifesto/ch01.htm