The source code for the GameCore DLL was only released in the spring of 2006, and Warlords was released in the summer of that year. The DLL expanded modders' possibilities a lot, so most of the widely used mods at present hadn't even started before WL. I wasn't a member here at that time; my impression from reading the old threads is that pre-WL modders kept their latest version available for some time – for players that hadn't acquired the expansion yet – and continued development based on WL. Same when BtS came out. Some of those old versions of early mods are still available for download, but I'm not aware of a collection of links.
moddb.com doesn't seem to have a separate category for the base game, nor does the CivFanatics download
database. However, browsing the database backwards could turn up some things. Like
this early version of Rhye's and Fall; the download seems to work.
On a quick dive into the
Inactive Projects, it looked like SevoMod might still be available. Development on that stopped shortly after WL came out. But, no, the download link is dead. Also – and I think this will be a common issue with mods for the base game –, SevoMod was apparently not compatible with the latest patch (v1.74) for the base game. That patch only came out in the summer of 2007. So one may have to downgrade to v1.61 to play old mods for the base game.
Going through my crib sheet of popular mods, the few that started before WL don't seem to have working downloads: Dale's Combat Mod, History In The Making. The Ancient Mediterranean might be on moddb in the BtS category:
https://www.moddb.com/mods/the-ancient-mediterranean/downloads
v1.95 seems to be for the base game, don't know if that's the latest.
Early versions of Realism Invictus could still be around too.
This list of "lost" mods contains mostly BtS mods, but here's one base game mod with a working download:
MaxRigaMod 5.3
Mostly a ton of new units iirc. (I briefly tried the BtS version years ago.)
I don't think highly of the new content in the expansions either (although it's arguably not worse than some random mod); I guess mods are the one strong point of the BtS expansion – the Better AI mod that was directly included, the mods bundled with BtS, some new capabilities for modding exposed to the DLL. Well, the bugfixes and misc. tweaks in the expansions and subsequent patches also seem noteworthy.
