Alot of hyperbole in here following a horrid performance. I'd argue that imo we're about 4 quality signings away from being a solid mid table Premiership side (injuries permitting).
An experienced centre back, an attacking left back, a winger, and a proper number 10. The latter two need to be creative to take away the complete reliance the current side has on Shelvey, and a good left back will complement Yedlin on the other flank and ensure 90% of our attacks down the left aren't wasted as they currently are with Dummett, and one good experienced centreback will be more than enough to solidify the defense with Clark/Lascelles/Mbemba/Hanley as partner. In fact, Lascelles and Mbemba already formed a competent Premiership partnership towards the back end of last season.
Whilst I understand the doom and gloom nature of some mindsets following a disappointing defeat and worrying performance against a mediocre team who were made to look like world beaters, lets not forget that according to some (many?) in here we were going to struggle to even compete for promotion since we didn't have this core of strong personalities that we had last time round, or that we hadn't signed proper proven quality goalscorers (Gayle was an unknown quantity, Murphy a mediocre Mackem). In fact, the last time we were in the Championship I remember many of us being completely down because of the lack of signings in the summer window post relegation (Lovenkrands the only permanent signing iirc), and even after promotion we were still going to struggle badly given the squad we had without major investment. And of course none of that panned out that way - so the glass half full view isn't always the right perspective. There's a few of things to consider as to maybe why:
1) Mediocre players can be useful, even in the Premiership. It's all about balance, and having enough good players to carry those around them. When we finished 5th under Pardew we had Raylor, Obertan, Saylor, Guthrie, Jonas, Best, Simpson, Perch, etc, in and out of the side.
2) A couple of good signings can transform a team entirely. Think Robert and Bellamy transforming a slow, boring, predictable lower mid table side into an attacking, free flowing top 4 team under Sir Bobby. Or Woodgate making Bramble/O'Brien look solid. Adding the right "something" can completely negate a weakness which impacts the team as a whole, and that something doesn't need to be changing an entire team.
3) A very common trait with fans is completely overlooking, or failing to understand the concept of, players improving with time and experience. Everything has to be here and now. People want someone proven immediately, failing that it's "game over". Sort of like that West Ham fan a couple of decades ago having a go at Harry Redknapp for displaying nepotistic favoritism by playing his 18 year old nephew who wasn't good enough, Frank Lampard. Closer to home Andy Carroll and Tim Krul are the most recent relevant NUFC examples of players declared my many at the time to be not good enough for the Championship, or the Premiership, and it seems to be the case that being proven wrong doesn't soften the lack of faith in players improving. FWIW I'd say Darlow, Yedlin, Clark, Ritchie, Hayden, Gayle, will all be Premiership ready by the end of the season.
4) Rafa Benitez is in complete control of NUFC. This man has won the CL, knows the English, Spanish and Italian leagues inside out because of direct first hand recent experience, and should we get back into the Premiership could well have a significant transfer kitty to work with. So that's a widely recognized world class manager potentially capable of attracting players through reputation alone, having money to spend, in probably the most attractive league in the world to prospective talent, at a relatively well known Premiership club due to having frequently appeared in Europe, and with a large stadium. I'd be surprised if we didn't get at least a couple of genuine top quality players in who'll do well in his system in that scenario.
I'm really not worried about next season at all with this squad and Rafa in charge. The only worry is getting back into the Premiership, especially through the automatic promotion slots. But I think if we add a couple of decent Championship calibre attacking players to the team whilst shifting those who want away (Tiote, Mitrovic), similar to what we did with Routledge/Harewood the last time we were here, we shouldn't have any problems.