The game isn't total shit, but its just not up to the level I would expect from a Neo shooter. The levels look and play all the same. It gets repetitive really fast.
This really sounds like you did play the game three times with credit feed and put it back on the shelf. Don't judge a game you didn't play thoroughly, especially not an arcade game. You could say this ("look and play the same") about almost every shooter you just credit-feeded a couple of times.
The game has its qualities like scoring, sound and boss design. There are some major flaws like boring backgrounds and the slight homebrew'ish feeling, but it's still a really good game. Playing it on maniac is a lot of fun if you try mastering the scoring system. Which, judging by the online highscore ranking, next to nobody has ever succeeded in.