They're not perfect (nothing is), but they're actually pretty good. Every task has to be completable within a sprint. If it's not, you break it down until you have a part that you expect is. Everyone has to unanimously agree on how many points a particular story (task) is worth. The process of coming to unanimous agreement is the difficult part, and where the real value lies. Someone says "3 points", and someone points out they haven't thought about how it will require X, Y, and Z. Someone else says "40 points" and they're asked to explain and it turns out they misunderstood the feature entirely. After somewhere from 2 to 20 minutes, everyone has tried to think about all the gotchas and all the ways it might be done more easily, and you come up with an estimate. History tells you how many points you usually deliver per sprint, and after a few months the team usually gets pretty accurate to within +/- 10% or so, since underestimation on one story gets balanced by overestimation on another.
It's not magic. It prevents you from estimating things longer than a sprint, because it assumes that's impossible. But it does ensure that you're constantly delivering value at a steady pace, and that you revisit the cost/benefit tradeoff of each new piece of work at every sprint, so you're not blindsided by everything being 10x or 20x slower than expected after 3 or 6 months.
Great that it works for you.
The truth is on most teams one or two people who are closest to the task have enough context to estimate, and probably only after they spent some time starting or prototyping the task.
Those people can give a reasonable estimate, in time not some strange point system.
Sometimes the estimate is wrong and that’s ok.
It’s fine to have a meeting catching everyone else up on the context but those pther people still likely don’t have enough to give an accurate estimate and shouldn’t be involved in estimation
But the fact remains that in most environments, it's extremely useful for medium-term planning and especially in surfacing high-risk features that can send people down the wrong path for a long time. And it's meant to benefit stakeholders -- the people paying the developers' salaries -- not individual developers. It's about de-risking.
And if you really have the kind of team you seem to describe where everybody only works on their specific type of task and can't even estimate anybody else's work, then that's a danger situation when they leave or get sick or whatever and nobody else can step in and everyone's blocked because the only person who can do X is gone. Usually, you should be actively getting other developers to work on these features (usually the easier/smaller ones) and involving them in the estimation.
To the developer, it seems like short-term sprint planning. But to the PM and stakeholders, it's very much medium-term planning because they're picking tasks for this sprint in light of what they also estimate the following couple sprints will look like (given current information, which is always going to change).
It's not as bad as it sounds, because when you're re-estimating something you already estimated in the past 2 planning pokers, it's usually pretty quick. You're just seeing if the previous estimate needs to be revised based on what the team has learned since. Most time is usually spent on newly proposed features, or features that have significantly changed or been split up.