May be it is important knowing traps in some openings. But i am sure that we often lose a game because of a tactical blunder, no matter the knowledge we have about openings.
and because it so much time consuming (to learn lines and variants), may be it is more interesting studying tactics, and endings instead,
Don't... Simple really :)
Look if you follow the general principles you should be fine and if you get caught by tricks, learn the trick there and then and dont fall for it again.
Your much better off spending your time elsewhere!
I used to practice against my engine using the opposite colour I wanted to learn. Play a particular line and see what it does. Then play those engine lines when you play blitz online. Avoid using the opening book for best moves and just play whatever you want and see how it responds.
If you come up against someone playing stuff that cause you problems, play them against your engine and see how to deal with it.
Over the years I've played quite a few openings and got familiar with different opening ideas. This is where bullet and/or blitz really helps cause you get to see a large variety of positions.
Once you get to about 2200+ on lichess, you might want to specialize and pick a few openings for tournament play. Spend some serious time on opening explorer on here and look at the main line and side lines of your opening and how to get an advantage against sidelines in particular. It might be worth working with someone if you want to improve quickly.
However, opening prep is only one part of the game and it's important to try and understand the typical middle and end games that are likely to emerge from your openings. No point prepping like a GM if you don't have the technique to close.