People take these kinds of things way too literally. There is no golden solution here. What gets repeated over and over continues to be true: teams should choose a system that works for them. And ideally that system is measurable, so the team can evaluate progress, improve its own performance, and align itself better with other teams and the business.
But in terms of scrum and points here's my take:
I've seen points work on some teams and not work so well on other teams. It's imperfect, but if you just accept that, you can make it work quite well.
The reason it's helpful to estimate complexity as opposed to time is that people with different experience levels would give different estimates based on their abilities. Complexity allows you to rally around a common understanding of a solution regardless of how fast one team member might be able to complete it versus another.
Does complexity have some relationship to time? Absolutely. Everybody knows this. That doesn't mean that we should be using time instead.
So how can a team estimate accurately? You will hear from some people that their estimates were wildly off or that it's impossible to estimate a project or they felt pressure to under-estimate. If your estimate is too broad, you need to do the mental work of breaking it down into smaller chunks that are easier to estimate. If you feel under pressure to ship on an unrealistic schedule, that's not a points/scrum problem. But the "it's done when it's done" is also not realistic either.
The idea that the estimate has to be 100% spot on is also not true. Again, it's imperfect and that is ok. But you'll find that the better a team knows their codebase and knows the product, the better they'll get over time at estimating. But if the work is too vague, the team should push back until they have enough information to more accurately break things down. This process makes for better software, especially when the team does it together.
Another missing aspect I see a lot is having a feedback mechanism. If you as a team are discussing why a task took longer than the estimate, or track metrics over time, you can all get together and figure out where problems on the team are. For example: maybe there are too many bugs that are hindering product work? Why? Maybe you're moving too fast vis-a-vis the expected quality bar. Some sort of feedback mechanism (e.g. retros) is crucial - the team as a whole should aim to deliver what it says it would and understand why it couldn't.
The whole point of these things is that as a team you can deliver consistently not more speedily. Consistency comes before speed. The other important thing is having a way to continually improve. You want to use each sprint as a way to measure the team so it can get better.
When I've seen teams that did this well, they were dramatically more productive than the teams that didn't do it well.