Toilets, Sinks, Showers, Tubs and Disposals - Amount of water in the bowl after flushing

Why does it seem like I have less amount of water left in the toilet now then before after flushing? Even if I were to slowly pour water down it would just drain away instead raising the water line.

Not a major issue I suppose but it just seems weird because all other toilets in my home isn't like that and can retain more water after a flush. What made it change?

If water is not disappearing as a result of draining water elsewhere in the house, you could have a crack or defect in the bowl.

Usually disappearing toilet water is being siphoned out of toilet bowl. If vent stack is partially clogged or clogged all the way, when water is drained through the drain/vent system, the water will drain out of the nearest fixture in order to create another vent. You need to check the vent stack for clogs. It might be that you have leaves or a nest of some kind in the vent. You can usually run a water hose down the vent to rinse it out. Sometimes you have to call a plumber if DIY is unsuccessful or you can not access the roof to reach the vent.

If I leave this unfixed would it become a bigger problem down the road?

If it is currently a partial clog that could eventually become a total clog, then the vent stack would be blocked and there would be no venting. Toilet bowl trap or other traps in home could be siphoned dry. Then, you have sewer gas (methane) inside your home. A properly working drain/vent system leaves water in all the traps to block out the methane. Methane is not healthy, and it can kill. Methane is also flammable.