u can’t sorryy gillyyy

Yes, you can.

If you have a direct link to the playlist, there will be a big yellow “subscribe” button.
Unfortunately youtube doesn’t make it easy for you to get these links, in fact, there is no button anywhere that takes you to the playlist page.

All you can do is watch the playlist in the authors channel or watch the videos one by one on the video page, you can thank the new youtube layout for these inconsistencies.

To get around this issue, find the playlist you want to subscribe to, copy the name of the playlist – and also copy the name of the author – then paste both into the search box and run it.

After the search you will be given additional options, click on “search options” and choose playlists as the “result type.”

Hopefully your desired playlist will be displayed in the first page, all you have to do now is click on the title to go to the playlist page with the subscribe button.