It really depends doesn't it on the player and their own ambitions and circumstance doesn't it? And fundamentally what they deem is a desirable trait when joining a club.
Robins is undoubtedly a draw, especially on the loan front, but looking at it objectively there's far more to a player's decision making when joining a club than who the manager is. Pay, location, ability to progress their career with/without the club, who they're playing with, size of club, club ambition etc.
It's such a multi-faceted and complex decision that unfortunately is largely dictated by what the club can offer - both in wages and in transfer fees when looking to acquire said players in the first instance.
I don't really think that us being in the PO final last year is much of a draw at all really. It's yesterday's news and nearly half the team that was present on that day will have likely moved on by the end of the window, including the team's two most integral players. Just look at Huddersfield season last season as an example to highlight why that just isn't necessarily as much of a selling point as you perhaps might think.