DeiaMari This might just be how Sims 4 runs now. Changes were made so that the game initially loads more data, the idea being that subsequent loading times would be shorter. If you've played a household for a while, it would make sense that the save has more data to load.
What you can try, just as a test, is deleting your main household in the affected save, plus any others you've played for more than a short time, plus any large builds, and really any builds you've downloaded from the Gallery. Use "save as" rather than "save" so you don't overwrite your main save, then quit and reload and see how long it takes. It would be a useful data point if nothing else.
If this helps, you can go back to your main save and try deleting only the sims, and, in a separate test, only the complicated builds and those from the Gallery