The question wasn't over their removal but over their replacement. There was unanimity over the need to have Warburton, Pedro and Murty leave but a clear lack of unanimity, bordering on ignorance, about who should replace them. That doesn't negate that opinion.
The board's managerial record since 2017 has been nothing but farcical: Warburton's messy departure; appointing Mark Allen after we had a manager in place; the appointment of Pedro - the most baffling signing, player or otherwise, in Rangers' history; the appointment of Murty; the unimaginative and expected pursuit of McInnes; McInnes' ultimate rejection; the subsequent extension of Murty's contract; the termination of Murty's contract; and the short-term appointment of Jimmy Nicholl, whose last job was at Cowdenbeath.
Call all of this what you want - naivety, cluelessness, ignorance, inexperience - but it deeply calls into question the quality, rigour and care exacted by the board in their managerial searches and invalidates the idea that there was so many "insufficient candidates of quality" that their only recourse was to appoint a youth team coach. Put simply, I wouldn't trust them in the hunt for a manager.
Again, I really don't think anyone in the team has sufficiently improved under Gerrard's direction, and it's interested that you've limited your examples to the ones I gave, spoken more generally about the team, and referred to Europe, which represents a fraction of our season. I think you'd struggle to find support in the idea that Gerrard has raised the games of Tav, Edmundson, Katic, Goldson, Polster, Flanagan, Davis, Ojo, Kent, Halliday, Aribo, Kamara, Barker, Jones, Arfield, Stewart, Hastie, McPake, and that's before we get onto guys he didn't think were good enough at all. It's been as massive disappointment in that area, and the lack of serious transfer bids for our players, and another abortive season, testifies to that. Surely if these guys were coming on leaps and bounds we'd do better in the league, not collapsing at the same point in January again and getting knocked out of the cup to a team bottom of the league?