As for the beer quality, so far most of these acquisitions haven't had a negative impact on beer quality. The more troubling aspect of these acquisitions is that they have a negative impact on smaller/local breweries in many ways. First is a lot of the InBev brands have engaged in predatory pricing to gain market-share. I am still able to get kegs of GI IPA for cheaper than Budweiser right now.
Another is they can wreck havoc on the resources available to brewers. A couple of examples, now that GI has greatly expanded BCBS production and they have InBev's resources they are buying up every whiskey/bourbon barrel in sight making it difficult for a lot of breweries to start or continue with their own barrel-aging programs. Another is that Elysian now has the buying power to basically buy out and monopolize many hop varieties now. Hop growers are already struggling to keep up with craft beers demand for flavor and aroma variety hops. It takes growers several years to establish crops, if Elysian swoops in and buys up every (for example) Simcoe hop they can find that will have a huge negative impact on many breweries who have beers with an established flavor profile.
Now I'm not saying for a business standpoint you can fault the "big guys" for taking advantage of their economies of scale. But from the perspective of a craft-beer enthusiasts who loves the current culture of craft beer these things are very damaging. This is why I try to avoid these acquired brands and to keep my beer dollar local whenever possible.