Well.. you are certainly right in that regard that it's frustrating if you just can't find "insert object of desire" for a long time. I certainly had the same situation with turnip seeds in the swamps without having realized that you can plant turnips to get seed plants.

However.. there are tools that can help you with that. No need to get frustrated.. for example.. insert your seed at valheim-map.world and only look for the elder location.

You can also ask for direct ingame help if you can trust random steam or discord strangers.

Imho if you really looked at so many crypts and towers.. I can't stop thinking that you are close to find one.

I hope you mark all your locations and dont end up at some stuff twice thinking it's new xD. I know I had some of these odd situations.