Ask HN: How does remuneration typically work within a startup?

I've been having a chat to a friend about their role in a startup and I would like to learn more about the process of remuneration from those with experience. I understand that it will differ from company to company.

Reason I ask is that they are quite attached to the company and have been working there for 5 years and (until recently) haven't had a pay rise, ever. This was odd to me because without the bare minimum of an inflation raise, they are actually losing money every year.

They had to speak up when they found out their co-worker was getting paid more for the same role (and was objectively less efficient at their role). They stuck with them (company) through tough times but now the company is doing well they are hiring others for the same role and those with zero experience are getting paid very close to what they are currently making. And that became another confrontation because they aren't looking after their long-term employees and were hoping they wouldn't say anything.

I get from a business point of view that if you're able to get away with paying less you will but this sounds like another startup that likes to treat everyone "like family" until they selectively choose not to.

What can one do in this scenario? Is it common for a startup offer "shares" in the company instead of straight money? Or for them to keep quiet about pay rises (like the last 5 years) and hope the employee never brings it up (performance review = lets review what you did without discussing anything about pay)? Is there something one can do to take advantage of this situation without risking them denying (or giving a little) pay raise and essentially "wasting" the last 5 years?