I've read a couple VNs with no good end, have yet to play any games with no good end. Bad end or good end is really only something decided by the developer at the end of a scenario, it's no more indicative of how things actually are than a straight game over screen. You'd be surprised how many supposedly good ends have plenty of bad connotations. What matters isn't whether it was a good or bad end, but why it was and how you got there
In your example, the game tells you how to win and gives you the tools to succeed so long as you put in the work, and then blindsides you with an ending that could be considered failure, that's not just a bad end but bad writing as well (and can apply in reverse, although it happens more rarely, you can have a game tell you that the end will be bad and then blindside you with a good end for no apparent reason). Good or bad often doesn't matter so long as the ending is well written
And even then, a well-written ending isn't necessarily what makes a game. The end is only a small part of the game's story, which is one of several pieces of the game. It's a very important part of what can often be a very important piece, but it isn't everything. A good ending can help color how you remember the experience, but it's unlikely to define it