When you are synthesizing designs using Vivado Synthesis, there could be situations when the runtimes are longer due to the constraint validation phase. Typically, it is due to the expansion of wild-card characters (*) present in the constraint file for objects related to set_max_delay constraints.
To avoid this problem, use separate constraint files for synthesis and implementation and move the backend constraints to the implementation constraint file. This will help differentiate synthesis and backend constraints, and also reduces synthesis longer runtimes during the constraint validation phase. In addition, reducing the number of objects that the wild-card * character can match can also speed up the XDC constraint processing and thereby reducing longer runtimes.