Is the Offense actually good?

Good players. It's a ideal situation for a GM and HC because there are some really good players on the offensive side of the ball before free agency and the draft. There's a difference between having good players and a good offense. We don't even know who our HC or OC is yet so how can we have a "good offense?"
These are good players.

Cousins (I hope we trade him) The new regime should be able to add a good QB.
Thielen
Jefferson
Cook
Irv Smith
Gronklin (if we keep him)
Darrisaw
O'Neil
Cleveland

Do the Raiders, Jaguars, Giants, Bears, Texans, Dolphins, Broncos or Saints have a better collection of good players on offense than the Vikings do as of right now?

I'll say this: the offense could be good, and really has no excuse to be this inefficient/streaky. They should be good with a better, more experienced OC who can adjust in-game.

Good like the Chiefs, Bills, Rams, Cowboys, etc.? Probably not quite yet, but definitely a lot more efficient. The three-and-outs with as much talent as we have truly is inexcusable. It was infuriating.

With it looking more and more likely we go with a younger, defensive-minded coach, I'm nervous about the OC pick ... and how long that OC will stick around if he shows an ounce of potential/innovation.

Maybe if our defense is borderline elite to elite in the near future (very unlikely). And with the way the NFL is trending with hotshot OCs, it's less likely our DC would be poached any time soon. A good year or two on offense and bye bye.

I'm going to add a few more to this:

12th in total yards [sum total metric]
14th in points scored [sum total metric]
11th  yards per play [average metric]
26th in 3rd down conversion rate [average metric]

The reason I added the sum / average call out is a 3 and out kills a per drive metric; it's basically putting up a 0 for that drive.  Same for 3rd down conversion rate, a 3 and out is just a 0/1 on that stat. 

The take away is that the Vikings are at or slightly above average on things like points and total yards, despite having a very high number of 0 value throw away drives.  This means that if a 3 and out is worth almost nothing to those averages - when they are not going 3 and out, they are much better than average.

So the real question to me to determine if the offense is good is: Are all these offense killing 3 and outs the fault of the players or the play calling?

Because the things are going very well when they aren't going 3 and out, my opinion is that the play callers had no idea on how to get the drives started.  So if a new coaching staff can not trip over their own feet on the first play, there is enormous upside to the offense. If new leadership can avoid a single 3 and out per game, the extra yards and points from that would easily push the Vikings into a top 5 offense.  Other top offenses are already avoiding those 3 and outs, so don't have the same opportunity for growth.  If the Vikings did avoid a single 3 & out per game, and add even a few yards, here is how they pan out
+10 yards per game = #9 offense
+15 yards per game = #7 offense
+20 yards per game = #5 offense

I think that is not a very big change to make, and given (at least) occasional stretches of questionable play calling, one that I think the Vikings can do.

This was the point I was trying to make. Well said. There's obviously something driving the 3 and outs that need to change, but when they move the ball, it's a very effective offense. And I think the eye test tells us that too. Most of us were pretty upset with the play calling, as it was way too predictable. Predictable play calling will lead to 3 and outs. Some of that can be blamed on execution, but to me that's a coach not knowing how to set his offense up to succeed. 

That is because they have more chances to put up more points and yards, which would be fine, but it means the opposition also has more chances to score more points and put up more yards.  

To your point, the Rams actually had a lot of 3 and outs in 2020, 11th most, and were 25th in ppd in large part because of it, had the 3rd fewest in 2021 and jumped to 4th in ppd.  Not because of a change in play calling, but because they improved significantly at QB. 

Seattle with Wilson as the QB and multiple OC's has been consistently bad in this stat, so it isn't like you have a bunch of 3 and outs and your offense is bad.  The big difference there is that Wilson is traditionally a slow starter and then turns it on later in the game, while our QB is the opposite.  

Also, a correction on the above. The Vikings were 31st in 3 and outs per drive, so the author didn't do a bunch of per drive metrics and then do a sum total for the last one in an effort to slant the stats in favor of his argument.