Barring the horrific start (0 from 9 points) and disappointing end (defeats to Brighton, Southampton, Tottenham and Newcastle) to last season (where we had a number of injuries to a squad that was yet to have Saliba, Zinchencko and Jesus added to it) - we racked up a serious amount of points. Our performance this season is the result of filling in the holes in our starting lineup that led to those two horrible runs. It's not a flash in the pan, we've been building towards it for a while.
Our squad is still too thin, to the point where a long-term injury to Partey would be catastrophic. But if we continue to make sensible transfers, I can't see why we wouldn't have the foundations to maintain our levels - we're the youngest team in the league. Partey and Xhaka are our only key players to have peaked. Almost all of our key players are 25 or younger. It's pretty unlikely that Jesus, Saka, Martinelli, Odegaard, White, Saliba, Gabriel, Zinchenko, Tierney and Ramsdale are going to become worse players with an extra year of experience under their belt.
That doesn't mean we're going to be successful in future seasons - or even this one. But if we don't win any trophies in the short to medium term it will likely be because other teams improve and raise their level to above ours. It probably won't be because Arsenal spontaneously combust.