Depending on the project team i would say selling just because the price is down and not because the team have stop supporting and developing the project is not such a good idea. those l1 blockchain you mentioned above aren't that bad imo, project like cardano, terra, avax, have strong community support and any project developed using these blockchains will not just die simply because the price of the market is down, except the dev team behind those project are not capable of pushing the project forward through the time of bearish market. if that is the case, then no harm in selling otherwise i don't think it is wise.
I am not certain how good Cardano is, however, there are users who mentioned that it does not work under situations where there are very many transactions. It was shown during the release of Sundaeswap. According to some social media comments, they had to wait for more than 24 hours for their swaps.
I agree that some of those mentioned might be good blockchains, however, the argument is the bear market and how this kills much of their ecosystems that causes users to move their investments out and send them back to Ethereum and Bitcoin.
Cardano is not widely used for transactions like bitcoin and ethereum, but on the other hand, I think Cardano is very suitable for trading because there will be profits in the gaps between rising and falling prices even though the market is in a bearish position.