Let's be fair about it further though..
Polish league is a good league yes. My comment was a little tongue in cheek. Go around Dublin, London, Paris, Madrid or any other major European city and ask a random 100 local people do they know who Jagiellonia are and what league they play in, and I'd wager you won't get too many correct answers. They're hardly a household name, much the same a Levadia Tallinn. That was the point I was making. The Polish league is well supported in Poland, it's hardly full of household names though?
Also, Jagiellonias average attendance last year was just north of 13,000. Only one team in the league averaged over 20,000, and that was Legia Warsaw. Lech Poznan were next on 19,000. They hardly 'regularly filled their 22,000 seater' at that?
I'm not trying to denigrate anyones level, far be it from me as a League of Ireland supporter to attempt to denigrate any level of football, as you say, stats don't lie and Ireland is sitting in a heady 36th place in terms of league ranking. The point is, Maguire is an in-form striker, and just scored a European hat-trick on top of his 19 league goals, and yet he still has to make a step up in leagues to be regarded worthy of a call up. I don't understand this. If he played five good games and scored five goals in that space at Preston, you can sure he'll get called up, and everyone will be (rightly) saying it's well deserved.
If he's in good form now, why not call him up now?
Every striker you mentioned above as current options are over the age of 30, or in the case of McGoldrick, turning 30 this year. Will Keane has given no indication that he'll declare for Ireland and has arguably yet to prove himself at senior level. O'Brien is playing League One. Are you saying that's above where Maguire is playing? Joe Mason is an average to poor Championship striker who's best league season to date saw a return of only 9 goals, 7 seasons ago. Grego-Cox reportedly has potential, I have yet to see him play, but he's got a grand total of 6 senior appearances and no goals. Turning 21 this year, that's hardly ideal?
For me, Maguire should be in the squad already. It's total bullsh!t from O'Neill to pander him off saying he's not ready yet.