[chongli]

Galaxies themselves aren't expanding, they're gravitationally bound. Galaxies are moving apart from one another, however.

The issue is that not all galaxies are moving away from us. The ones that are closer to us have a lot of peculiar velocity [1]. This means they can be moving toward us or moving tangentially to us or any other direction. If we want to characterize the expansion of the universe as a whole, we need to account for this in our models. It turns out to be a lot more complicated than we previously thought.

The crisis in cosmology (aka the Hubble tension [2]) is that our two means of characterizing the expansion of the universe, models of the cosmic microwave background (CMB) and measurements on the cosmic distance ladder using standard candles (Cepheid variables [3] for up-close measurements, Type Ia supernovae [4] for more distant measurements) disagree with one another, and that disagreement is getting worse, not converging.

[1] https://en.wikipedia.org/wiki/Peculiar_velocity#Cosmology

[2] https://en.wikipedia.org/wiki/Hubble%27s_law#Hubble_tension

[3] https://en.wikipedia.org/wiki/Cepheid_variable

[4] https://en.wikipedia.org/wiki/Type_Ia_supernova