[graftak]

jQuery is immune to modern optimisation techniques such as three shaking (only including the modules actually used) because it’s fluent interface makes it a gorilla that holds quite a few bananas, even if you only need one of the bananas.

[ryanbrunner]

I would imagine the percentage of front end projects that have a build chain sophisticated enough that tree shaking is important and where 30 KB has a significant impact on their bundle size is vanishingly small.

[WorldMaker]

Tree-shaking isn't a sophisticated feature with ES2015 modules and it's more surprising today when build chains don't support it. (The sophisticated features come into play doing any sort of tree-shaking on older module types such as CommonJS or UMD.)

It's not even a build-chain only feature at this point. Some of the reasons the ES2015 module format was built the way that it was were exactly so that browsers can do their own tree-shaking of runtime code. Even if you don't save on the performance impact of the extra 30 KB from being downloaded, in modern enough browsers you would potentially still see a performance impact on browser memory usage and JIT compilation time.

Even if your bundle size has bloated to a MB already, a 30 KB savings is still roughly a 3.3% savings. It's still noticeable. Whether that is "significant" is an argument of personal taste and how many "9s of performance" you try to deliver. Even single digit percentage savings can be huge "significant" wins for many projects.