Last time I played EVE was almost 8 years ago. Back then I could support myself in Null by running missions for Angel Cartel in Curse with my Tengu. As I remember correctly you could earn LP and buy valuable implants to sell in Jita afterwards. As I understand lots of things changed since then, and I’m wondering is it still a viable method of earning ISK. If yes - which pirate faction to choose now?
The missions and LP stores are unchanged. The market value of the items in the LP store probably has changed and the cost (in ISK) to PLEX your account has gone up a lot.
Missions are some of the oldest content in Eve, there is newer PVE content like the Abyssal sites that are probably more lucrative but all PVE is a repetitive grind - nature of the beast.
Pirate faction missions are still available. There are also burner missions which were added since your time and you can do in frigates. You can also do the epic arcs. As for what is most valuable I am not sure. I have done Serpentis and Angel ones. The Serpentis are worth more but have only a couple level 4 agents in all of eve which gives you less choice of missions to do when you want to. The Angel missions are given out by many agents so you can stack up missions you like easier. Similarly, Mordus Legion might be more valuable but again have few agents in a small area.