You can assess during the game. Are the same calls made on both ends of the court or not. While you see palms and travels all over teh court these days, when you see one team called and the other not.. nearly back-to-back.. there is something odd about that.
Also, you can account for the possession calls made in lieu of a foul call. Those, too, happen all the time. Then in the final two minutes that fails to work to even things up because they can go to videoreview where they cannot then call a foul because that would have been the right call at the time.
You also see some situations where one team gets "continuation" or a delayed foul call until they shoot and another team gets the call "on-the-floor".. not a shooting foul.
You see refs making late calls based on "no harm, no foul".. or so it seems. You see them watching if the shot is altered or will go miss before they whistle.. or if the ball is retained or lost.
I cannot say if it would be a better game to WATCH if they made more calls and instantly do so. I think they could easily justify doing so because they are out there to enforce the rules of the game. The more they allow the more that encourages teams to do more of the same... more pushing and shoving and grabbing and reaching in and palming etc etc etc. I suspect if there were constant calls then after some time, players would play more cleanly.. like the old days.
But, clearly, the more they allow the more infractions occur (with or without calls) and the more CONTROL the refs can have re: the outcomes by choosing which calls to make or not.
The "same calls made on both ends" is one part of it, and speaks to some level of bias - but that's more rare, in my experience. Usually it's just gross inconsistency - which may impact one team a bit more than the other, but it's not an intentional slanting of the table.
One ref might get it in his head partway through a game that he's going to "clean up" the banging underneath - and call a couple of quick fouls. Now, one is a fluke - players might easily think it's just a one-off call that's inconsistent with the tenor of the game - but two back-to-back is generally the ref sending some sort of message that the way the game is called is changing going forward. However, if the officiating goes right back afterwards to allowing that sort of banging - it's just sloppy and bad officiating.
Same with things like hand-checking, palming, moving screens, push offs, block/charge, etc - players get a sense of what is and isn't allowed early on in the game (and having seen a lot of these refs before, they know their tendencies) and adjust their style of play accordingly. Sudden, jarring shifts can cause significant impacts as players scramble to keep up with the ever-changing officiating landscape play-to-play... which is just poor officiating, and we see it far more often than we should at this level, imo.
Of course black-and-white things like out of bounds, goal tending, back court/shot clock violations, etc aren't judgement calls and should always be consistent game to game (but sometimes aren't - frequently in the same games as the other inconsistent officiating, which speaks more to incompetence than just "being human").