1. They're traveling in a medium, so they move slower than in space
2. Due to the random walk caused by multiple scattering, it can take millions of years for a photon to escape the sun after bring produced in the core.

You are right that they don't gather energy, but they do multiply. What would be a single high energy x ray in the core will eventually downscatter into an army of optical photons.

It can definitely take millions of years for photons to leave a star due to dense protons causing collisions.

https://futurism.com/photons-million-year-journey-center-sun

For photons, their moving relatively slow from the inside to the outside of the sun. Although, I think, it's technically a bunch of photons bumping each other into existence.

... they definitely don't move slowly through the sun.

They kind of do. While the photons inside the Sun move at a very high speed, they can take up to about 170,000 years to get from the middle of the Sun to the outside, because they change directions a lot on the way.

also temperature doesn't really exist at that scale.