I'll always support the team regardless of the manager, but here's why I think Karanka is the wrong choice.
Hasn't managed in England in just shy of four years. He left Birmingham perched above the drop zone when he did.
At 51 years old he'll be the oldest manager we've had since Tony Mowbray, not that this is old by any means, but in a footballing landscape that's getting younger and younger (McKenna/O'Neil/Hurzler/JDT/Eustace) I'd much prefer a younger boss.
His connection to Rudy Gestede is concerning, this smacks as "jobs for the boys". I hope Gestede knows he's putting his own burgeoning reputation on the line with this appointment, the success or failure of the two will be linked.
It also feels like the cheap option. I agree you should be looking for value, but with supporter numbers and season tickets on the wane, taking the cheap option will hardly inspire supporters heading into the final 12 games and more importantly next season, our 150th Anniversary year. Lack of investment in the squad and coaching staff ultimately leads to lack of investment in the stands.
The way he left Middlesbrough and Nottingham Forest. Both times Karanka left because of issues with the board, having lost our last two managers to effectively the same issue, it feels like a ticking time bomb already.
His only Championship success came at Middlesbrough in 2015/16, next season that's 10 years ago. For context when he had his best moment in English football, promotion to the Premier League, Steve Bruce was also promoted. If your argument is "he's done it before" then the same applies to Coyle, Bruce, Hughton, Wagner, Jokanovic all promoted with clubs around the same period.
The snap poll from yesterday gave a worthy indicator of the overall thoughts of the fans. https://live.tiermaker.com/34616583 as of this moment 83% of the fanbase voted negatively to Karanka becoming the new boss.
Combine this with many Rovers' fans feelings (based on recent experience) that the playoff push will fall short, any negativity now will no doubt be amplified come the summer. For any good will towards AK he'll have to hit the ground running. This could be argued for any Rovers boss, but at least some good favour would buy 'him' more time.