With Finland -- I assume, from your username, that you are Finnish -- NATO mostly avoided that in that they basically just skipped any kind of long-running accession process (which, given the situation with Russia, I think was probably a good idea). What happened, as I understand it, was more-or-less that Finland got added and people said "well, we'll work out any issues after Finland is in".

https://www.euractiv.com/section/defence-and-security/news/finlands-real-integration-into-nato-might-take-years-officials-say/

Finland may now officially be a member of the Western military alliance, but the full integration process will still take some time, officials told EURACTIV.

Realistically, the actual move could take up to two years, a NATO source briefed on the discussions told EURACTIV.

As obnoxious as I think that Turkey's objections to Sweden's membership have been, they also weren't something that Turkey sat on for years on end after Sweden applied and then pulled out down the line. Sweden applied May 18, 2022. Turkey issued their objections the same month. That's a veto, but it's also not a veto that waited around to be pulled out until after Sweden had done things that Turkey wanted; it's comparable to what I was talking about above with an EU member needing to raise their objections up front. Now, maybe the concessions Turkey was asking for were not reasonable (I certainly think that some on political speech in Sweden were not), but that's another story.

That being said, I think that there's a separate issue for NATO of a country effectively having to disclose that they're aiming for NATO membership; it's not really possible to keep the thing secret. The tactic that Russia used with Ukraine -- make use of a period where one thinks that a country is likely to join but has not yet joined, then aim to preempt membership by preemptively-attacking them and occupying at least part of them, holding territory as a hostage to try to block entry -- is legitimately an issue there.

There were security assurances issued by a few countries independently of NATO in Sweden and Finland's case, as I recall, but I think that there's a broader issue that the whole model isn't ideally suited to counter a party who might just attack a country any time it looks like they might join a different defensive alliance, else one could imagine the situation in Ukraine being repeated elsewhere. Maybe there needs to be some kind of temporary guarantee issued for the duration of any NATO MAP; that might be hard to keep truly secret, but at least it would be possible to limit the window during which a country might be attacked. That alone wouldn't address the issue for Ukraine -- Ukraine wasn't in a NATO MAP at the time that Russia attacked -- but it'd solve part of the problem. Something else would have to be done to deal with attacks that come before any MAP exists.

On the other hand, NATO needs to have some kind of expectation that a party is actually going to move towards doing anything that needs to be done to join. Say Austria or Ireland wants to join. They have a constitutional mandate of neutrality (which has caused political complications for the EU's mutual aid clause). They have to revise that, and that will be a public political process that takes time. NATO providing some kind of guarantees for the duration of the process might make sense (though neither one is likely to be attacked by Russia, given the existence of states between them and Russia). But, okay, say a revision attempt fails -- the government of either country cannot guarantee success, cannot simply revise the constitution at will. Then what happens? I mean, NATO also shouldn't be obligated to permanently extend protection to a non-member that isn't going to become a member with no reciprocity in place. But, that country will have divulged interest in membership. And maybe an attack isn't such a big risk for Austria or Ireland, but there are other countries for whom that is a considerably-more-prominent concern. I don't know if there are necessarily answers that handle all the edge cases. I do think that it'd be possible to at least improve on the existing situation, though.