Google's John Mueller confirmed on Twitter that it may be worth looking into compressing your HTML and CSS. He said "Sometimes minifying HTML & CSS can reduce the size of the files, so it can certainly be worth looking into that," when he was asked if it can help with SEO or rankings.
Of course it matters how bloated your pages are right now and if GoogleBot is having issues consuming the content on your pages or consuming all your pages within your site. But overall, tweaking things so your pages load faster is a good thing not just for SEO but more so for your users and conversions.
Here are those tweets:
Sometimes minifying HTML & CSS can reduce the size of the files, so it can certainly be worth looking into that.
— 🍌 John 🍌 (@JohnMu) June 30, 2019
Forum discussion at Twitter.