Getting past the event horizon of a small blackhole is tough, the gravitational gradient causes spaghetification. However larger blackholes lessen the gradient at the event horizon, so it's not a problem.

Not sure about the inner horizon, just saw a discussion of the paper for a spinning black hole recently, it described three distinct regions.

Most lay-person discussion of black holes just ignores the spaghettification and radiation problems. Those don't really have anything to do with space-time or information propagation or cosmology or such, those are just limitations of material strength and biology.

The discussion is more like, if we had infinitely resilient materials or biology, what could they observe and experience.

> what could they observe and experience

Observe? Nothing, once you're inside the event horizon, right? The event horizon isn't a solid wall, it's just the point at which light can only move further inward, never outward. So even inside the event horizon, we still can't observe anything further in.

“Spaghettification” only happens to large enough objects near small enough gravitational sources. If the Moon got too close to the Earth, closer than the Roche Limit, then it would break up into a ring of debris. But a communications satellite can exist at that same distance with no ill effects.

The same is true for black holes. A rocket or a human diving into a stellar mass non–spinning black hole would be “spaghettified”; they would be broken up into a thin stream of debris as they crossed the Roche Limit before they crossed the event horizon. But they could cross the event horizon of a much larger black hole, such as a supermassive black hole at the center of a galaxy.

In fact, if the black hole were massive enough then the gravitational field near the event horizon would be so mild as to be Earth–like. If you were to stuff all of the mass of three or four Milky Way–type galaxies into one black hole, you could build an actively–stabilized structure around the black hole to create a livable environment of truly insane proportions with Earth–normal gravity. Look up Birch Worlds sometime.

> you could build an actively–stabilized structure around the black hole to create a livable environment of truly insane proportions with Earth–normal gravity

Which was also a rocketship into the future, moving you super fast towards the heat death of the universe?

Not exactly. Time does run more slowly near a strong gravitational source, and if you are near the event horizon of a stellar–mass black hole this effect can be extreme. However, the larger the black hole is, the flatter the space around it. Furthermore, “near” is relative. A Birch world would be built around a black hole which is approximately a light–year in diameter. The structure would be “near” the black hole’s event horizon in relative terms but in absolute terms it would still be pretty far away, perhaps a quarter of a light year. Expect a time dilation of just 2:1, meaning that for every year on the Birch world two years pass for the rest of the universe.

It might seem like this costs you a lot, since it halves the amount of time you can live near your black hole. However, the lifetime of that black hole will be somewhere between 10¹⁰⁰ and 10¹⁰⁶ years, which is pretty insane even if you only get to use half of them. Furthermore, this is many orders of magnitude longer than the lifetime of a galaxy, so your civilization could potentially outlive everything else in the universe. Large stars burn out the quickest, but with black holes it is the other way around: small black holes evaporate the soonest. You might think that storing hydrogen in brown dwarf planets for use in fusion reactors would power a civilization for a long time, but fusion reactors are surprisingly inefficient. A civilization built around a rotating supermassive black hole can take advantage of the Penrose process to extract more usable energy from the same mass than the fusion reactors would.