Does that make it good?

Single issue voters, like those who only vote for/against abortion, are literally throwing aside every other issue. It’s a disservice to themselves and a disservice to others who have to live with their decision.

Switching to a third party which agrees on a subset of topics with the original party they come from is completely understandable. But again, doing a complete 180, especially knowing what parties stands for in the US is hard to believe. It should takes years, and I mean more than a decade.

It depends on what matters to people. In the US, there have been a number of significant platform shifts in the major parties over the last 10 years. Think of Trump vs mainstream Republicans, or the shift in the Democratic party from support of racial equality to support of racial equity. These are foundational changes that can completely alienate large blocks of voters.

In fact, I would argue those least likely to switch parties are the single issue voters (esp. gun control or abortion) since the parties have not shifted on those issues. Whereas blue collar whites have been abandoning the Democratic party in droves lately despite that being their home for a century. It started after Clinton signed NAFTA, but has really excelled over the last 5-10 years.

Also, a lot of people vote a split ticket where they support people form different parties depending on local/state/federal or even if they just don't like a candidate in their preferred party (see the difference in votes for Walker and Kemp in Georgia for instance).

Single issue voters are incoherent politically and not relevant to any reasonable discussion.

No, it is not the case. There is no coherent political position which exists between the American democratic and republican parties. Anyone who believes they exist in such a middle space is lying to themselves.