Agree with you completely.
Relegation would diminish our club, possibly destroy it. In the long-term it would turn us into a Luton or a Sheffield Wednesday at best.
It all depends if we can bounce back up in the first attempt. If we can, then damage will be limited and we might be able to come back at the same level (if player recruitment is successful).
Other alternatives include becoming a yoyo club and getting sucked down further like Sunderland.
There's a good chance of all these happening but I'd say scenarios 1 and 3 are most likely given our financial situation.
We have been horrendously mismanaged (I predominantly blame the Koeman wasted transfer kitty). But our problems go beyond this. Unlike what would have been possible in previous years, we can't just throw money at it. This scenario has purely been manufactured by the clubs who just so happened to be good in the 2005-present era. Precisely to prevent further competition.
The game, like everything else, has become a huge multinational corporate machine where only a handful of clubs have any realistic chance of winning anything. It's just shy of the American closed shop model. We also just so happen to share a city with one of these bloated capitalist behemoths (at least Newcastle don't have this disadvantage). This will make it so much harder for us to ever gain traction if we get stuck in the lower leagues. We could become your Notts county to your Forest or Munich 1860 to your Bayern.
It's just so frustrating that we wasted the money that had initially been pumped in and the stadium we've been waiting for didn't happen soon enough. Whilst the owners have been wasteful, the timing of this is very unlucky.