Yes, beginners should focus on long time controls; Ideally, 60 minutes per game, or even longer. You need time to think about everything you're learning, and blitz just doesn't give you that needed time.
For tactics training, if you can't find the tactic after several minutes, you should just look up the answer and try to remember it for the next time you try the position. After a number of attempts at a position, you should be able to spot the tactic within 10 or 15 seconds. If you can't do that, then maybe the tactic is too difficult for your level.
For some reason blitz seems very popular online.
Me being a beginner, it seems like a very bad thing to do as I still need to think about even the simplest of moves. I still need to analyse the board and make sure I do the correct thing.
When I play vs computer, I average out at around 15min and I still lose on easy games :)
I can only imagine what would happen if I start playing blitz games...
I also find it weird that the tactics trainer is focussed on time... I often have the correct move but I lose rating because I took me to long.
Is chess really so time focussed or is this purely because of the popularity of blitz?