How intense and serious a dating simulator can be is your choice depending on what you want.
If you're looking to play a classic game some time to expand your dating simulator knowledge, True Love is still a fun play through.
And they often have time limits, so you have to keep your goal in mind.
Imagine a visual novel meeting a choice-driven role-playing game - that's the basic gameplay of a dating sim.
You take control of (usually) a character played in the first person, so that character can be YOU.
Then, in whatever plot and setting the game has, you choose which person you want to try to romance and win the heart of.