Here is a good source to decide which altcoin to invest in. I would never buy a dead altcoin with no development except Doge. Doge is unique and will be successful without much development.

Source:
https://twitter.com/el33th4xor/status/1068856384983363585?s=21dead alts are:
- Verge
- Holochain
- Bitcoin Private
- Pundi X
- Poet
- Decentraland (MANA)
Well of course! Who would invest on a project that is not active? No one! And also when investing, not just the fact that the project is only active but also has a good qualities that will surely give you good profits on your investment at the future.