In general, I am pro-turnover where there is rivalry: ceteris paribus keep the newer thing. However, information is so cheap as to be effectively non-rivalrous so I am considering running my own archival and to keep kagi's small sites etc. alive. Unfortunately, there is not a good tool for this that matches whatever Archive.org has. ArchiveHub needs routine management to keep the feed up and viewing it is not that easy. I'm sure we'll come up with stuff.
The other thing is that searching for the long tail is near impossible. The big sites dominate Google, so I need something like marginalia to actually get to the old stuff that it used to be so easy to find. Because of the median user having simple queries, some questions are no longer answerable on Google: they are dominated by the median user and never show up.