Cryptocurrency Historical Data Snapshot. Many top altcoins in 2013 now no longer actively developed and can be considred as dead altcoins.
You can back read some of the discussions there but it's not that active at all unlike the other top altcoins like ETH that has a lot of posts into its thread.
Cardano has its own forum for
$ADA did made a x20 growth in the last bull run and from today price $0.38 to its latest all time high, you will have good profit.
You're right that many successful projects after going on in the forum abandons their thread because they own one after their success. But still, the community that owns their coins/tokens are discussing and continues it there. Maybe some interesting addition to what they've discussed can be extracted there.