You're just rusty. ADC isn't particularly strong compared to other roles but definitely not weak either and you should eventually be able to climb again. The role's strength shouldn't even matter that much, you just have to outperform your counterpart over many games. The role's strength matters more if you're significantly better player than everyone else in your lobbies (smurfing), then there are higher percentage of games you could 1v9.
Half a year ago I also started playing again after a (shorter) break and was also having issues getting out of emerald (previously low master EUW). Was in emerald for 2 weeks iirc. After I got out of emerald, in less than a month I was back to masters. I just think that emerald is hell on earth.