It seems to be that creating Polygons in 2.1 is much slower (roughly 5-10x) slower than 2.0.7.

The following script takes roughly 0.1 seconds with Shapely 2.1 and 0.015 with Shapely 2.0.7. This is on Python 3.12

import time

import shapely

if name == "main":

start_time = time.time()
for _ in range(1000):
    coords = ((0., 0.), (0., 1.), (1., 1.), (1., 0.), (0., 0.))
    polygon = shapely.Polygon(coords)

print(time.time() - start_time)