Alright, so spoilers.
I think that the people killed in Infinity War should stay dead. People right now don't believe that Marvel killed them off permanently, because some of these characters have future movies announced and actors with known filming schedules, but let me address those and how it's still possible to move with what we know of Marvel's future plans. I really do think that these characters should stay dead, too. It would be an incredible move on the part of the MCU and something that people truly would not have seen coming, and in the long term they will get a lot of praise for it. It would be the most ground-breakingly bold thing that they could do. Now, as for dealing with some of these future movies.
Shuri, inspired by her brother, becomes the Black Panther and stars in a female-led superhero movie.
The new Guardians of the Galaxy will consist of Rocket Raccoon, Teenage Groot's twin brother (because Groot left a lot of other twigs lying around), and the new Guardians of the Galaxy group headed by Sylvester Stallone (which was the original team from the comics, or so I've been told).
The confirmed Spiderman sequel will have Tom Holland in it, but the twist will be that he will play a shape-shifting symbiote who is obsessed with Peter Parker and impersonates him. Yes, there's already a Venom movie coming out, but studios have reached the point where they realize that audiences can handle there being more than one continuity. Through some flashback or comic-book logic, we'll see how Venom also managed to gain some of Peter Parker's memories. The movie will be about how the symbiote tries to replace Peter Parker without anyone noticing. Some people from The Avengers get suspicious.
Either that, or the whole movie is a prequel between Peter and Uncle Ben. Let's face it, it isn't officially Spider-Man until there's a seen between him and Ben with Ben telling him that "With great power comes great responsibility."
Doctor Strange traveled into the future to do some things before Thanos ever killed him, so you will see a time-traveling version of him who hasn't been killed by Thanos yet. This was the version of Doctor Strange that saw the one version of the future where they were able to do anything useful. Eventually, he will have to travel back into the past to face his death. His movie isn't actually even officially announced, so we could potentially just not have a Doctor Strange movie. Alternatively, his not-officially-announced movie should be scheduled far into the future, after this next particular point.
Perhaps Marvel could undo the deaths from Infinity War, but I think that it should only be after a long while. They should build up a fresh new cast, have several new Avengers movies in-between now and then. Perhaps even turn Infinity War into a four-parter. Then, for Part IV (which would be Avengers 6, for those not keeping track), we finally get all of the dead heroes back after a long, long journey. But the post-apocalyptic universe with half of the heroes dead should be the status quo for at least six years. It should be like in Samurai Jack, where the heroes actually fail in perpetuity until some distant series finale. So even if the consequences of Infinity War aren't truly permanent, they should last for a long time.
Then, when they eventually come alive again, you will have three different generations of heroes all teaming up to make for one epic Avengers crossover, perhaps as the ending to Phase 6 or something. This giant crossover with three generations of superheroes could also include the X-Men, which can now fit into this world in a logical way if mutants popped up in the post-apocalyptic era. Seriously, though, Marvel should take their time building up to that. The only downside is that Tom Holland will return a bit older, but we'll get to see how teenage Peter Parker would have hypothetically grown up in this world through his symbiote impersonator.
Do it, Marvel. I dare you.