And better rocket come 'space ship' preparedness. You can only learn so much about things from millions of miles away regardless of your resolution. It's a very serious problem that our space program has severely regressed. In 1969 we put men on the moon and brought them back home safely. In 2019, we struggle to send a man on a flyby around the moon!
It's frustrating because we already have the technology to be able to achieve basic intercepts here, even if they were at high velocity. The only thing in the way is a dilapidated space program.
Manned exploration may have reached a zenith in 1969, but science did not. In 1969, the field of planetary science did not really yet exist. Since then, we have done flybys of every planet, intercepted comets and asteroids, put orbiters around many of them, landed probes on more, and even had robots driving around! A ton of science has happened since 1969.
We also learn far more from robot/probe missions per million dollars spent than manned missions. The Mars rovers have explored for years on end (albeit slowly) while a manned mission to Mars and back may only be able to stay for a few days. I personally would love to see us walk on the Moon and Mars in my lifetime as I was not around in 1969, but the science can be performed just as well if not better with modern robotics without even needing to bring them back.
This is a particularly good example of the problem.
NASA provides regular updates from Curiosity here. [1] What you might find there is that problems are never ending and that progress is very very slow. As an example one of the primary missions of the Curiosity rover was to try to drill into the surface of objects on the planet to start getting some basic idea of what was going on. The problem is that after superficially activating the drill 15 times, it broke. The drill feed mechanism became disabled. The most likely culprit is some dust or other particle caused a critical brake to get stuck. This is a 10 minutes fix for a human on site. For the rover? Countless minds at NASA spent years working out a solution and came up with a solution that is not really sustainable and still leaves major issues with sample collection. That solution, limited though it may be, is as much a testament to the capability of NASA's engineers as it is to the major limitations of probes and rovers. The Planetary Society had a really nice write up on this here [2].
Opportunity recently died after more than 15 years on Mars. An absolutely remarkable achievement for a rover with a planned mission length of 90 days! However, even then it's death may be premature. One of the most likely culprits for its demise is that after a substantial dust storm, which it went into hibernate during, its solar panels were left covered with dust. A Martian janitor with a broom could fix in about 10 seconds, but for a rover - it's time to enter the long sleep. Another side of the story is that during its long life, Opportunity was only able to travel 28 miles, a bit less than 2 miles a year. You end up getting a very limited view of what's going on. Curiosity, for comparison, has managed 12.5 miles of travel in its 6.5 years since landing.
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Finally there is one last major point to be made. We don't know the cost of manned missions. We can speculate on the cost of sending the first man, but I mean once we actually get into the 'normal' phase of putting men on other planets much as we do to e.g. the ISS today. We currently spend about $70 million per person to send them up, and that's a greatly inflated price as we rely on foreign suppliers. But even at that price, sending a man into orbit on a station intercept for $70 million is something that at one time would have been unthinkable.
We will likely see that price drop the single digit millions of dollars, at least in real cost, before the end of this decade. And getting to orbit in space is 90% of the battle. There's an old quote that once you get into orbit you're halfway to anywhere. And that's pretty much true. There will be a serious up front cost for setting up habitation systems but once these are established, I think there's a very strong argument to be made that humans will quickly become cheaper than rovers.
And finally this all completely ignores the human aspect. Putting a man on the moon shaped an entire generation of people with hope, optimism, and a sharp increase in the drive towards scientific pursuits. In a world of needless division, petty diversion, and increasing pessimism towards pretty much everything - you can not overstate how monumental an effect there will be to once again start putting people on other planets.
I would not disagree, though the Soviet Union had already put a probe within the atmosphere of Venus in 1967. In 1970 they landed a probe on its surface!! They were called the Venera [1] probes. They also returned audio and picture from the surface of Venus. Absolutely remarkable if you're never heard it before. This [2] is the sound of the probe coming down through Venus' atmosphere, its landing, the lens cap (for the camera) popping off, the deploying of the drill, and then the drilling of course. In my opinion that remains arguably the most remarkable achievement in planetary science in our solar system. Although it must be said that that audio came much later than the earlier probes. "Much later" being about 40 years ago.
I think the recent discovery/confirmation that our moon has substantial reserves of water ice emphasizes the difficulties with technology outside of manned exploration. There's a lot of information you can obtain from probes and other forms of remote observation, but it tends to be extremely specialized and very limited. This is not something we should be discovering 40 years after landing on it -- water was confirmed in 2009.
It's frustrating because we already have the technology to be able to achieve basic intercepts here, even if they were at high velocity. The only thing in the way is a dilapidated space program.