The layout of your rivers seems to be physically unrealistic in many cases (rivers branch and rejoin and sometimes appear to be flowing uphill or through mountainous terrain where there seems to be a shorter option to lower terrain). The biggest visual river problems are just to the left of center. The rivers down the valley form large loops around islands. The primary rule that "water flows downhill by the steepest route" doesn't allow for large-scale river features such as this to form or to remain stable over a period much longer than a few years (such as might occur during the formation of an oxbow lake).
It isn't naturals waterways but canals, digged to cut the meanders.

Do you have a scale for this map? Many features of river and mountain systems are scale-dependent and it would really help in an understanding of the map.
Done

And now the progress of the map:

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