So, if helium is light enough to escape Earth's gravity, why don't we use helium balloons to go to space? I mean, these guys [0] are trying to take a rocket to the edge of space using a helium balloon, but there's still a good old-fashioned rocket involved.
"Going to space" is a lot more than merely getting out of the atmosphere. You need to get orbital velocity, and a balloon isn't going to do that.
For an individual helium atom it's possible to pick up enough velocity to escape Earth's gravity. When they're all tied together in a balloon, that's not going to happen.
You pretty much can take a balloon to space. You'll pretty soon fall back to Earth though, as you'll be nowhere near orbital velocity.
Getting to space is easy. Staying there is hard.
For example, if the ISS passed directly overhead of you, it's only 250 miles away. I've driven three times that in a day. The trick of the whole thing is that while it's only 250 miles away vertically, it's moving at 4.7 miles per second laterally. It goes around the Earth (roughly 25,000 miles) in 90 minutes. It's going to be hard to get your balloon to those kinds of speeds.
When you say humans "goto space", you're probably talking about going to orbit. As such, the problem isn't that space is "up high", it's that fast is "very fast".
This "XKCD What If?"[0] explains this concept pretty clearly.
[0] https://www.bbc.com/news/uk-wales-49827415