i can only speak for myself but...
ps+ has not stopped me from buying a game i really want day-1.
ps+ has not stopped me from buying games (if anything i buy more and digitally due to the awesome ps+ discounts).
...for me, my spending is about the same but i'm getting more games for my money. i think i'm buying more games at a cheaper cost overall (and playing some of the free ones) and overall playing more games. BUT,. when a game is bad i don't give it much of a chance. i used to play everything i bought out of principal even if it wasn't a great game. now if it is only mediocre i just move on to the next game.