Trouble is that lot's of people do onboarding poorly. What you and the parent comment call out is a failure mode: to build effective onboarding you need to understand who you're building it for and what they're trying to accomplish. A tooltip tour approach might be effective for certain kinds of products/users/use cases, and extremely ineffective for others.

What I've seen be most effective (at least for B2B SaaS products):

1) tailoring the experience so people are being onboarded in ways that are relevant (e.g. their role, are they the first user or nth user, their use case/job to be done, how familiar they are with the domain/similar products, etc...) and

2) do>show>tell: get people to use the product to learn how it works vs plastering signs all over it. Which modalities are most effective is product/user/context dependent.

Source: I've been responsible for onboarding at a few SaaS companies now (and am now building a platform in the space)