Earlier I read a post claiming that summoning being added as a skill would not be “oldschool content” as compared to what? Jagex released summoning in January 2008 and the game devoured it. It wouldn’t be “OP” because before the EOC update, only 17k users had 99 summoning in a game with 150-200k active users. Summoning would be the only viable and logical skill addition in terms of keeping the game oldschool orientated. Also it would be good for the game for various reasons. 

It could become a huge gold sink (which is very much still needed), it could revive PvP which is beyond dead (anyone who PKs would agree), and it could bring back loads of players back to the game who are tired of playing because there is nothing else to grind because we haven’t had a skill update in 10 years?

The only argument is that there are other skills that are more fun to train like dungeoneering so we should add dungeoneering instead of summoning but realistically we already have dungeoneering rewards as buyable items in game.

tldr: Summoning was a great skill. It was fun to train and made the game more interesting in terms of gameplay style.