Google's John Mueller said on Twitter, "Page size is not a ranking factor." Meaning Google does not have anything specific signal that says page sizes of X to Y get a ranking boost or decline.
John did add, "(I'm guessing the HTML file? or the total loaded bytes? either way.) It's fine to look at this though, and it could have implications on page experience (core web vitals) and crawling."
Of course, if your page sizes are so big that users, browsers and bots chock on the files, that can be an issue. But finding pages like that are generally rare.
Recently, John also said that core web vitals should not be a priority for most small businesses. John also said previously that CSS size does not generally impact rankings either.
Here are those new tweets:
Page size is not a ranking factor.
— johnmu is not a chatbot yet 🐀 (@JohnMu) March 8, 2023
(I'm guessing the HTML file? or the total loaded bytes? either way.) It's fine to look at this though, and it could have implications on page experience (core web vitals) and crawling.
Forum discussion at Twitter.
Update: Later on Mastodon John added "I don't see it as a factor at all. If we separate document size (words/sentences) from response size (HTML size), for response size there's a cut-off of 15MB, but no preference below that. For document size, it's more a matter of understanding what a page is about, what it should rank for. (Is the random mention 5% from the bottom important?)"
