Crx4Chrome is still active and functional. When you are on an extension page, it shows up to 10 old versions. To view more older versions click on "More Version History".
To each page shows 10 versions. Go at the bottom of the page, to navigate between the different versions when there are more.
In the example of ublock origin, the oldest version on the site is 1.9.10 while the latest at the time of this writting is 1.27.10. See images below.
Note: Although the oldest version was on page 6, it is not listing versions on that page from 51 to 60 but still 1 to 10.
Disclaimer: I used ublock Origin as an example of an extension I used whose versions are listed on the site. I am just a user of the extension, not related to the developer(s).