A captured Bok globule.
The tricky part here is the "will affect all ships landing on this planet [...] they have been designed to reach orbit from similar planets." clause, since I read that as meaning that future ships should be able to freely land, and communicate, but will know in advance that they will be unable to take off, even if their mission is specifically designed for this particular planetary destination.
This precludes economics/time as a concern, as well as just about all of the existing suggestions, so far as I can see. Anything unexpected that subsequent ships can be made aware of, or that ground crews can clear from a landing zone; anything that attacks material, fuel or people that could be shielded/protected in subsequent landers; volcanic effects (rocketry doesn't care); weather (would make landings harder than takeoffs); energy leeching (can't think of any approach to leeching where energy brought down in the ship couldn't be protected, apart from handwavey "the beam is sucking power straight out of the dilithium, Captain" type soft-science stuff).
Our big problem: in general, landing in one piece on unstable ground or in an unstable atmosphere is harder than taking off and reaching space from a solidly built base under the same conditions. Given enough notice, ships can be made secure against whatever threat that would prevent liftoff. The only exception is that liftoff takes more energy, and that's a difficult one to prevent since energy can be brought down and protected.
So, what about if we reframe the question. Perhaps what we really want is the "Bermuda triangle in space". A place that ships avoid, if they accidentally enter they are never expected to leave, where their navigational instruments will be useless, they will run aground, and will never have a rescue ship sent because it's known to be dangerous; but which nonetheless happens to be reasonably pleasant if you're wrecked there.
So, is there some method that can make a planetary system act like a lovely atoll amidst hostile uncharted reefs?
Kessler syndrome has been suggested and allows us to destroy the ships, forcing them to crash-land on the only viable planet; or to send out farm-more-strongly-protected escape capsules which can survive (or be small enough to mostly avoid being hit). But typically Kessler syndrome happens on a planetary scale. For this to work, it needs to be on a stellar scale instead: the whole solar system affected, perhaps more.
Put the planetary system in a big ol' cloud of electrically charged space-dust and radiation blocking comms and visibility, so they won't know how Kesslery the area is until too late. Then it just becomes "that dangerous, uncharted nebula around that one star". Ships avoid it, and try to steer clear. If they're forced to take a shortcut through it, they either pass straight through without turning, or they get hit. Ships lost in there are assumed to be lost forever.
Problem with normal nebulae: if it were the original nebula of the star's formation, then the planets that formed would have cleared the dust away, any remaining dust would have settled in the disk, and there'd be no problems.
So likely this would need to be a small, dense dust nebula that the star has recently captured or is passing through. The nebula would need to have these properties:
- Not many dangerously large life-ending chunks that might hit the planet and destroy all life;
- Enough smaller chunks that a ship passing through the system stands a decent (1%?) chance of being crippled, but the route might just be worth the risk for some risk-takers or outlaws;
- The small chunks would be accelerated by planetary gravity, so it'd get exponentially more dangerous as you approached the planet (making "running aground" there a near-certainty if you got too close?);
- Lots of radio interference to mess with communications so mayday messages can't be detected from outside the system;
- RF blocking interference also affecting navigation, electronics, object tracking, etc, like an old sailing ship having its compass messed with while in a fog;
- Blocking visibility for tracking smaller objects, for laser comms, and for rescue ships to find deserted ships, thus making rescues impractical given the danger;
- Allowing the planet to be old and temperate enough to support life;
- Not blocking the light from the sun enough to prevent life on the planet, though it can have cooled a good few degrees from a desert planet to a temperate one as it went deeper into the cloud. By feeding on the dust, the sun could also get a bit brighter as it entered the nebula, compensating for the dimming of its light?
Bok globule
These seem to fit a star drifting into a filament of what is called a "Dark Nebula", or perhaps the small subtype of dark nebulae called a Bok globule.
Narrative benefits
This answer also has some visual/storytelling benefits, too. All that space junk it's passing through will give a constant show of shooting stars and incredible aurorae across the entire planet, both effects being perhaps even visible during the day. The radio interference could perhaps even be accompanied by space-lightning; not sure how that works in space.
It also allows for other dramatic story elements: drifting "space hulks" in the nebula; other stars within the nebula could endanger the planet's parent sun, giving a longterm motive for finding a way offplanet; outlaws might hide out in the nebula, avoiding planets as they would accelerate space debris, increasing the risk significantly.
Plus, "Bok globule" is just a wonderful name, and you want to be able to use that in a story.
Speed of light
This one's not a great answer to the question, but... the planet could just be a long way away, and not reachable by any other ships. Then any ship which crashes there will never see a rescue ship. This feels precluded by the assumptions in the question, but I thought I'd offer it as a possible solution just in case, anyway.
