The reason the web is not fun anymore is because it's now hypercentralized. Companies that effectively control the web found the formula that works for them. They want you to mindlessly consume streams of curated information. They want you to do that at maximum throughput. Most of your "interactions" with websites are fake and exist only to improve "engagement".
If everyone starts fiddling with colors and creative designs, it will decrease the throughput of an average information consumer. Therefore, no meaningful customization is allowed. It's that simple.
If everyone starts fiddling with colors and creative designs, it will decrease the throughput of an average information consumer. Therefore, no meaningful customization is allowed. It's that simple.