Also it depends on what sort of project Wenger is selling him. I'll be the first to admit we need to sign a CM this summer AND Lemar along with what we already have to challenge for the title. Its unlikely we'll do that, but we're changing a hell of a lot on and off the pitch. 6 huge changes so far and we've only just gone on tour.
You have to remember we were only 3 points off you's and 1 point off Liverpool last season. That was our worst season for 20 years. To get 75 points out of a season that bad is mind blowing. If we keep what we have, add the striker we've craved in Lacazette and also a solid left wing back going forward and back in Kolasinac you can't help but think that only adds to the 75 points from last season?
On top of that if we were to sign Lemar you then have the attacking depth to deal with all competitions. We're still a CM short of winning the title but we aren't as far away as people think with the current squad.
You're right, you wasn't far off both us and Liverpool but everybody in the league bar Chelsea and Spurs until they lost at West Ham and gave up was poor. Chelsea, City and United all had new managers and was expected to suffer from transition and all did at various stages, Chelsea just less than everyone else and United considerably more. Arsenal have had the same guy for 20 years, it was there for the taking. With a more settled squad and them more used to the managers style and tactics you can only speculate that all 3 of those teams will substantially improve and that's before player reinforcements.
I know next to nothing on Kolasinac in truth so i won't judge him but you're at least trying to rectify the weakness, lets assume he's solid enough and capable, Bellerin on the opposite side is very good too, Koscielny i think is vastly overrated but he's comfortably good enough but alongside him? All of your options seem quite weak, Mertesacker will have his uses in certain games against certain opposition but his pace and tank like turning circle leaves him very vulnerable against tricky strikers, Gabriel and Mustafi aren't up to scratch by a long shot. Holding can seemingly do a job but as a backup not as a starting centre back. So there's definite need for a couple of signings in defence. Midfield is your biggest problem though imo. I don't see a single player good enough to be a starter for a title winning side.
You could argue that if he truly wanted the champions league he would've moved to Bayern and happily been there for 200k a week, I think that's a huge factor in this. No doubts City are going to be strong next year but I can't see you winning the champions league.
I'm not disputing Bayern are comfortably ahead of us at the minute but they're in the process of going through a bit of a transition, a lot of their reliable old guard are moving on and their replacements aren't doing it just yet, they probably will in time but they're not currently as strong as they have been recently i'm not sure they're a team ready to win the CL in the next few seasons. I'm not saying we are, but it's clear to see we've got some phenomenal talents and are only heading in a positive direction. We were naively knocked out in the quarters last season on away goals by a Monaco side who every top club in Europe is eyeing up their players this summer and the summer before we narrowly lost out to eventually winners Real Madrid, via a deflected own goal so whilst i acknowledge there's a gap, we're not a million miles away as fans of rivals teams would suggest.
The biggest thing though and something i think your fans are underestimating is the Pep factor, Players want to play under Pep, particularly attacking players and more so players that have done before.