It is true that Turkey was a part of the Korea conflict. But back then, it was a country still influenced by Mustafa Kemal, which was stongly secular and one of the great leaders of the time (he still would be one, had he been alive today!).
Since then, there has been a couple of coups, the invasion of Cyprus, amongst other things, like attacking kurdish organizations who were fighting against ISIS. Even some quiet support of ISIS, if one is to beleive certain sources (like members of the US congress).
There is also jailing of critical journalists, and of political opponents (the mayor of Istanbul was a high-profile one example, recently). The beating of protesters at a Turkish state visit to the US is another example. So, ever since Atatürk, Turkey has changed. It is, sadly, not the same nation as it was back then.

Neither is NATO the same organization as it was back then. At that time, it was to work against communism and the Soviet Union. Communism is gone, so is the Soviet Union. NATO has become a organization which promotes democracy and freedom more than one to combat communism at all costs.

Still, it has the right to veto, as it still is a member. Though, I wonder how many of the current members would have been let in by Turkey now, if they hadn't been members already?

I used to be all for a NATO membership. But if it means supporting Erdogan, changing our constitution, having political courts and having no free speech, we would only remake ourselves in the image of Erdogan. Then it is not worth it. We will then instead strengthen our defenses on our own, and if we then die alone in the defence of freedom, so be it. It is preferable to being under the thumb of a pseudo-dictator, or real dictator, of any nation.