Every acceding EU member knew the deals and obligations. They accepted them, that is if they even barely read them and didn't skim the "nasty parts" in favour of the new shininess on the horizon. There are many problems which Dublin did not solve and outright ignored them because simply it was one of those things that didn't evolve around trade and commerce. Spreading asylum seekers according to one member state's population looked nice on paper would have ultimately failed because of the freedom of movement thing which the EU abides too.
Ultimately every member of the EU is bound by international human rights agreements which makes it even more difficult because the solutions which some parties are looking for are really lacking the humanitarian aspect in favour of "keeping the flood at bay". The Faustian deal which the EU made with Turkey is about the only and best short-gap solution they could come up with in order to prevent something that would have stained the EU and a lot EU members, Germany foremost, further for sitting things out and trying to exempt from responsibility and leaving a few "unfortunate" border states fencing for control whilst also being cash-strapped due to austerity obligations whilst also daisy-chaining humanitarian crises.
Italy and Greece, and even Spain, have been dealing with this far longer than 2015 (the year in which Merkel issued the statement). It just happened under the radar and the motto: "Thanks a lot for living 1500 km away...and if you want to hear my most noble-of-all advice: Drown or shoot these animals, please, or take it up with PETA - the NGO responsible for these...wretches (
I am a human, btw, best human EU too).".
Unfortunately it's all the result of ignored warnings, the conflicts in the Middle East are finally coming to fruition and then there's the warning of millions of climate refugees from Africa looming on the horizon which always has been warned before since the early 1990s actually. Nobody can't claim they didn't know about it and that they didn't have time to counter-act.
So? As per this
journal entry there is no obligation for asylum seekers to apply in the state where they first entered only that they can only apply once because the first member state in which the applicant files for acceptance would be obliged to take care of him. There are discretionary clauses which even allow making exemptions on humanitarian grounds. Hungary wanted them to apply in Hungary whilst most of them wanted to apply in Germany. Which is not what Hungary would have been able to do under the current system, in fact they even didn't want any of them to apply anywhere in the EU at which point they would have been obliged for lodging and giving out temporary-stay visas whilst they could have otherwise simply have deported them, cue in the new shiny NATO fence.
If the treaty explicitly stated that you could only make applications in the first member state you were entering then things would have been different. The system did not work efficiently or properly and it was constantly under criticism of the ECRE and UNCHR and her saying that or not wouldn't have changed much in the long term. That isn't to say I agree with her making this ad-hoc statement given there has been zero preparation or legal ground work and procedures done for that, given that it was pretty much a U turn of her - one of many and that she fuelled right-wing populism with the way how things were handled after or how things developed. She should have done that step 7 years earlier and much of this chaos that ensued would have been prevent and probably Dublin would have looked a lot differently.