Okay, i will try to keep it short since its too much work .
System is ok but its not rly enough, i know most game are better compatible and require less power but thats simply the crappy base the old team left and the new team got to work with. The thing with gathering is not for everyone but i for my part like even if its abit slow.

Putting effort into something should be normal. Maybe its too much for you for what you get in the end but its just a game. Synthing is fun for me, i like to find out what i need and where to get it and using the synth system the best way to get either HQ items or just alot of them in a short time.

Since you knew that a new team got to work on this, i dont know much about programming but when you get something whats finished then you cant just rip it out hack it into small bits and try to assamble it again.
The problem with alt+tab is something (i believe) rooted deeply in the corecode off xiv, maybe someone else can give you a more specific answer. But anyway with current game and current server its not possible. BUT will be possible with 2.0 btw.

2.0 is basicly a new game what they worked on and are working on while implementing new things into ffxiv and listening to feedback. If you dont like the current game version at all come again in a few months when 2.0 is out.
And i dont believe you have to buy FFxiv again to play 2.0.