Light coming in around front door?

Some weatherstrips may need to be folded out or bent out a little for them to seal against the door properly...try running a finger in the weatherstrip to fold it out a little and see if it seals better. There are a lot of different door weatherstrips with differing thickness or cross section/height that may seal poorly in some cases if not exact replacement ones.

You may also need to adjust the door latch striker so it closes the door slightly tighter to seal better....try pushing on the door when closed and see if the gaps close up...light stops shining through. If so, what I usually do is slide a large screwdriver behind the small metal tang of the striker in the striker latch opening and bend it slightly so the door latch is closer to the door stop and the door closes tighter against the weatherstrip....try to bend it a little at a time and recheck gaps....do not adjust it too far and make the door knob/latch hard to turn or open. You can always bend it back a little bit by tapping in the other direction with a hammer and punch or screwdriver...or remove the striker and bend the tang with a pliers or vicegrips...reinstall and recheck gaps. If your style of striker does not have a metal tang for adjustment...most do., replace it with one that does and adjust as needed or remove the screws for the striker, insert toothpicks and wood glue in the old screw holes...let dry and reposition striker so the latch closes the door slightly tighter and reinstall screws...usually just need to move an 1/8" or so. Adjust the deadbolt striker as well ...if the door has one...or file the edges of the hole areas if needed so it slides easily due to the new door closing position.

In some cases, I also may pry the weatherstrip out of the groove it sits in slightly to seal better...use a putty knife to pry it out and recheck gap as you go.

Remove the door, remove ALL the existing weather-stripping, and start over.....it was clearly never done right the first time....

You might consider paying someone who knows what they are doing to do it!

You made a rookie mistake. You fit the weather stripping to the FRAME instead of the DOOR. You need to MOVE the weather stripping so that it contacts the DOOR in the closed position.

Note: OEM means Original Equipment Manufacturer. The term DOES NOT apply to building construction.