Endgame was the conclusion of an era and the fact that it didn’t have a post-credits scene shows that. This doesn’t mean that the MCU is finished but that it’s the beginning of a new chapter.
The future MCU movies will see a shift, showing the impact of Endgame and how it affected the lives of every single character. This will be witnessed mostly with the original members who most probably will never really be able to move on.
The fans are going to have to wait to really find out what the original avengers will move on from this and if they’ll stay on the front lines or instead take a step back. Taking a step back doesn’t mean that they’ll be leaving the MCU but they’ll most likely be training the next generation of heroes.
Since, Endgame closed the door on a decade long saga. For some people they have been waiting for this conclusion for a significant amount of time. The experience of not knowing what’s going to happen while watching the film is extremely important.
Spoiling the film might give you a momentary feeling of pleasure but it would ruin the whole film for them and take away their ability to really immerse themselves into it. 10 years is a long time so if want to really spoil, don’t, keep it to yourself. Don’t be the Thanos that snaps away their joy.