Litecoin hype was died when their own Founder decided to sold his holdings long time ago when the price is on ATH.
Yep, after Charlie Lee dumped his coins into the holder, LTC is basically "dead." It might not be an instant death, and there's still a pump, but it can't rise over its previous market cap position.
Moreover, too many coins have similar purposes, only for payment, such as Bitcoin Cash, XRP, Doge, etc. So #20 on the market cap is actually good, considering how outdated the technology is.
I don't think LTC will go beyond its ATH, and it doesn't have any purpose at all you're right that it is only used for payment transactions but I think that more people will switch to much faster and less fee transactions. And I would say that LTC will surely go dump its price time after time if people will no longer invest or use it for transactions.