Frameworks are designed for the following (this is obviously an incomplete list):
1. large teams (not just one webmaster, circa 1999)
2. tooling like syntax checking, style enforcement, minification, and transpiling
3. component-based development & reuse; forces smaller files which are easier to lint and test
4. separation of concerns. in the old days there was one Apache www folder and everyone took a big shit in it. javascript was in html files that also contained php, it was snarled mess. frameworks separate that to a large extent (one could argue angular/vue etc went backwards)
5. regression, aka CI/CD: there are actual testing flows today, unlike the 2000s
6. if you've been out for a really long time: reactivity. JavaScript allows getter/setter methods that can update the DOM when a value changes; this includes before/after and around-like methods that can integrate AJAX calls in a VARAIBLE name. e.g., you access the variable and an AJAX call fires and updates your DOM when the data returns with you doing ZERO coding. This is a big step over PHP where you sprinkle magic server commands everywhere, and big step up over Jquery, where you have to target each DOM class/ID, which is tedious.
That being said I maintain a LAMP site, a pure-NodeJS site (get() verbs send back pug templates), and a NuxtJS website. I prefer developing the NuxtJS website (hot loading is sweet), but I can hack the LAMP site in a snap without touching literally everything; the NodeJS website is more aesthetically appealing in terms of architecture, but adding content to it is laborious.
EDIT: I'd go even further and say there is way more of a diaspora today. In the old days you could approach any website and basically understand what was going on in the frontened. Today there are layers upon layers of compiling/transpiling/parsing etc, that creates dozens of bespoke syntaxes. It is maddening, but I chalk it up to the fact that companies hire for the "hot new thing," damn the consequences, because their PMs are youngins too. There's a enormous lack of engineering discipline everywhere you turn. You will find many, many, MANY of the tools fail to even succeed at their own how-to guides because they have no real deep thought behind them.