I neither love Dak, nor hate him.
To me, he is an NFL franchise QB, and ranks in the 8-10 range of NFL QBs.
One quality I do believe he possesses is strong leadership.
When he received his previous deal, which was the highest for a QB at that time, he still had potential to get much better, and that is something that NFL teams must pay for (look at Herbert's deal for example, as he is not the best QB in the game, but he has so much potential). Today, Dak is what he is IMO. A good to very good QB (who has done little his playoff opportunities).
So Dak, be a leader, and don't expect to reset the QB bar, because frankly, you don't deserve to.
If Mahomes is making 45, Dak should accept something in the 40-45 range, and give the team the ability to keep and add talent around you (since frankly Dak, you're not good enough to win without a LOT of talent around you)
I'm saying this as a Dak fan, but it is the truth.
Brady made a lot less than other QBs most of his career, so the team could keep and add talent around him.
Dak needs to be a leader. The franchise showed you respect and gave you the top contract in league history at the time. I know others have surpassed that, and I'm not suggesting a pay cut. Just keep your deal in the range it is, maybe even a little bump to 45 APY, and be a team player. The goodwill that would come from such a move alone could make up for any "loss" in the form of additional endorsements.