Returning player here...

I left the game when they cutoff pvp, but now planning on returning for the pve because there's some additions there which is interesting for me. I know the game was so much free to play before, but how about now? Is the grind too much for epic relics? Can f2p players still clear nightmare runs? I had many champs upto 3 star when I left the game, just curious will it be a hard grind if I want to enjoy playig high star champs.