Again, there is no reason to give an advantage to those who can play it whenever they can, and by that chasing away all others that are the majority of users.
Giving advantage to those who are willing to spend some time is IMO actually a pretty good approach. And in no way does the transfer list system chase away the majority of users. There is a good supply of most types of players at almost any given time. Either you can find a good player that has his deadline closing when you are online, or you can check for players three days in advance. You can go into bid war right away, or plan ahead for the next time you log in. Doesn't sound too hostile against the majority to me.
For the absolute top teams, or for managers that want something really special, the market is of course harder to play. I see no issue with the really top talent being difficult to find and get. I am not sure if getting the top talent would on average get easier with auto-bidding. On the other hand, I am quite sure that the be-online-or-pay-what-you-have approach at least adds one element over the just-bid-your-highest approach of auto-bidding.
Let's get back to the majority of users here. What usually helps keep them in the game is keeping things simple. In BuzzerBeater's transfer market simplicity rules. All bids are final, and you bid what you want to pay. Any change to this system would only make things more complicated. You can argue that an auto-bid system is not that difficult and you would be right saying so. But it would still be more complicated than the current system. Taking that step would require some clear improvement, which I don't believe has been demonstrated with this suggestion (or the countless identical ones before this). There are opinions and preferences, yes, but these are not very factual.
Of course, I too have "lost" very good players (some highly unique even) because I was not online when the bidding ended. Tough luck I say. And I will never know if auto-bidding would actually have won me any of those "lost" players.