Why is Mexico allowing everyone to enter?
They don't enforce immigration control policies due to corrupt government officials. The southern Latin countries pay the Mexican government millions to take on their refugees. Nobody wants them so they allow them to pass through Mexico so it's an American problem.
The Mexican government does not care about it's people, only money.
On paper they have rules, but they are not enforced. Similar to the USA, but less strict. Nobody cares. The Police won't do anything. Only the military enforces the immigration laws and they are few and far between.
They need all the money they can get, so being a revolving door helps them with taxes for goods and services.
Right now anyone can walk across any Mexican border with no ID. Just pay 10 pesos (50 cents). Millions of people cross every day, most are Mexican citizens looking for work.
The USA border at Mexico is closed to non-US citizens entering here, so i have to have my passport for that. Me and my GF can cross anytime, but her family cannot come to America because they aren't citizens, but they do have travel visas that can't be used. It's a Covid policy that makes zero sense.
I go there with my GF every 3 weeks to see her family in Chihuahua City.