How much do ui libraries slow down the application?

Question

React

Previously, projects always wrote the entire uikit themselves. Now we are thinking about whether to try using the ui library.
Let's take Vuetify as an example.
Some say that they can't even live without such libs.
Others that it makes the app very slow. I wanted to ask if this is true? Doesn't tree shaking help in such situations? In theory, nothing particularly unnecessary should be dragged into the prod bundle.
And the components in any case will be implemented either by the hands of our team, or taken from the lib, so as I see it, if the lib is done correctly, then there should not be such problems. Or am I missing something?)

Answer 1

Braking and traffic are two different things. If it is important for you to save bytes, write your own and save. If your target audience lives where 3G is new, write your own and save. If not, do not engage in nonsense, but choose convenient tools.
The same applies to "braking". If your target audience uses low-budget smartphones up to $200, you will have to optimize. Otherwise, don't be fooled.
As lays down, then profile. By the way, Vuetify has an a la carte mod. Tree shaking works there.