It's an endless runner mobile game so of course it is terrible. Except for this one... because it's Pac-Man.
Pac-Man is not some mere retro arcade game. It has survived as long as it has because it is genuinely good and really fun. Pac-Man 256 really gets what makes Pac-Man good and translates that to an infinite maze really well. The ghosts all have clever, readable patterns and the thrill of navigating the maze is right up there with the arcade games. Plus, the game scores you on dot chains so you are always trying to evaluate the risk vs reward of continuing a dot chain vs breaking off and moving somewhere else or taking a turn that goes to an empty chain breaking spot.
Of course, since it a mobile game port, you have special abilities and a grind to unlock and upgrade them. Combining that with the randomness of the whole thing makes it a bit obnoxious to consider playing seriously for score, but if you enjoy playing Pac-Man at all, Pac-Man 256 is a worthy time-waster. It is certainly more true to Pac-Man than Pac-Man CE DX and CE 2.