You should not expect a good onboarding process at your company. Helping new employees ramp up is a good example of something that is important but not urgent. Tenured employees likely don't remember what it's like to be new.
While many companies will have insufficient or non-existent onboarding, the other end of the spectrum is also unfortunate: larger bureaucratic companies will have excessive onboarding, with months of training before you can do anything productive.
Even if the company has good intentions, building a solid onboarding plan is a hard problem: the tech industry's rate of change is very high, with people, tools, and technologies changing every year. Naturally, documentation and processes around onboarding become outdated.
Despite the difficulties, poor onboarding can be seen as an opportunity for new employees to have an immediate impact.