I believe exclusives were always seen as a good thing. Complains were coming usually from platform owners that lost exclusives like the N64 or the Saturn due to their lower market performance, hardware or license peculiarities, or when some company got exclusive rights from a franchise that was usually multiplatform or exclusive on a different system. So you bought for example a Nintendo console to play Final Fantasy only to find later it wont show up on that but on a different platform. Exclusive games were enjoyed a lot during the 32 and 128 bit era and we always wanted exclusive games for our hardware.I remember only not that long ago exclusives were seen as generally bad for the gaming industry. Weird how the narrative on that has changed and now it is the main reason to buy a console.
Trust me if Microsoft went out on Netflix-like spending spree on getting exclusive content for it's platform there would not be "Great!, now I have a reason to buy an Xbox or use Windows Store". There would be outright condemnation and "it's stupid that isn't available on every console" and "when will it be available on Steam?"
But if we go farther back, there was a time when exclusives were indeed a problem because of the amount and way a platform holder was getting them against competition. During the 8bit era Nintendo were using unfair competition practices, which stripped the more capable Sega Master System from content. Any developer who made games on NES had to accept Nintendo's terms that the game will not be released anywhere else.