There is no "best" art (sorry, high art world), but there are absolutely choices you can make for marketing rather than artistic reasons.
I like Robert Zemeckis and Ron Howard films, but they're boring ideas, well-executed. And I have a sneaking suspicion that given their copious directorial output and uniformity of end product... some of those choices were made for monetary rather than creative reasons.
Nobody says "I want to make a mind-bending Dune film, get me Robert Zemeckis!"
That is fair. I believe it's also the case that when evaluating art, it's easy to conflate those reasons with one's own POV and demographic biases.
In other words: Forrest Gump is cynical pandering to Baby Boomers... but [this-year's-Marvel-superhero-movie] is an artistic gem, and The Dark Knight or Black Panther got robbed at the Oscars, etc.
"ars gratia artis" doesn't apply to Forrest Gump. It was manufactured out of marketing data. It was the 90s version of most recent nostalgia film "Ready Player One". I know it won a bunch of awards ( which I put no credence or value on ) but it is film saccharine. Forrest Gump is one of the forefathers of the current movie industry.
What you call "exploiting a demographic" is more like "having a target audience instead of trying to be all things to all people". Sure, Boomers are a huge generation. But they were entering their 50's when Forrest Gump came out... and studios usually aim at 18-34 year olds because that's who spends the most time and disposable income at the movies.
What you call "Spielberging" is probably just a combination of cinematography, soundtrack, and accessibility over hipster snob appeal. In other words, good mass-market filmmaking.
Maybe this particular movie isn't your cup of tea, but there's nothing negative or cynical about this. "Cynical" would be hijacking HN threads to bring up urban walkability, UBI, random potshots at Baby Boomers, or any of the other standard hot buttons that typically guarantee upvotes and validation.