Pagination is part of it but most of it is simply using inefficient JavaScript frameworks and not learning how the DOM or CSS really work. The maximum number of

Pagination is part of it but most of it is simply using inefficient JavaScript frameworks and not learning how the DOM or CSS really work. The maximum number of elements you could have on a phone a decade ago was measured in hundreds of thousands (median) or millions (iPhone), and the hardware & browsers have gotten faster. The problem is that you have had a lot of very turnaround focused developers shoveling out code which uses deeply nested elements, poorly-scoped event handlers, etc. which mean that too many DOM elements are created, unnecessarily touched during updates, and the overall complexity means that on the off chance someone opens their browser’s profiler they won’t see a single obvious problem and will likely proclaim it unfixable and say something like “the DOM is slow”.