25 Million Euros is a fair deal for him.
Not that high and not that low, his weakness is he not versatile, this might make him not able to adapt in other teams. In other teams, midfielders are people who can help to attack and defend, but Dumfries play more defensive even as a midfielder.
Denzel Dumfries' release clause is considered too cheap so he could potentially leave and the clause will also be active this month. If I'm not mistaken, interested clubs only need to pay the price without having to negotiate with Inter Milan in a way that is too complicated and in conditions like this it will be very detrimental to Inter Milan, especially if they intend to keep Denzel Dumfries in the long term because he does have a good future.
The seven goals and three assists that he managed to provide last season are a very sweet record and he also has the ability to help attack even though it is not as good as some other players, but if you look at his performance in the Champions League last season it looks so good.