You're new. You're supposed to go easy until the instructor is confident you aren't a hothead and aren't going to hurt his other students. However, with the "wimpy" students, while much depends on the culture of the gym, you could just ask them to go through with more realism. Or, you could approach the instructor, and mention your concerns.
re: Aggression and physical factor; wimpy
I know what a lot of people mean when they use this phrase, but not everyone. You should qualify what you mean. Because often when people use this phrase, they're looking for the "fully resisting" opponent, and that can be just as unrealistic as a "fully compliant" opponent. On the flip side, "wimpy" is also subjective, and doesn't really tell us what you are truly experiencing. Sometimes when an opponent appears to be "wimpy" , that is just them waiting for the right moment for you to apply your "resistance", in order to reverse you. That is a common defensive strategy, but all of these adjectives you're using are very subjective, and without qualifying what you experience, it's hard to objectively understand.
re: Aggression and "physical factor" again
Be careful here, you need to train more and think less. Aggression leads to fatigue and execution of techniques which will land you in jail, or, at the least, allow your opponent to "up the ante" and respond to your aggression. If you were hammering on for points, that'd be one thing. In self-defense, you need to preserve your stamina, and focus on being anywhere in the world except where you're at. If you can leave, but you feel that being aggressive is the better option, you are no longer in a self-defense situation. Indeed: your adversary now has the legal edge. Your goal in self-defense is survival, not winning. If your goal is to be better than the other guy over machismo, perhaps boxing or some such is better for you.
If you're in the US, get used to the training not being like it is in Israel. Much of what is in the US is not like what it is abroad. And what is often offered for civilians is not what is offered to soldiers and LEO.
It's a sport, it's not meant for self-defense. In no boxing ring do they teach for weapons, multiple partners, and a great deal many other things. Sport is not meant for self-defense.
That is not the end-all-be-all place. Many times, what you see is a showcase of the best of the best. You should not expect to be at that level at this stage of your training. Trying to get there too soon will cost you in technique, so don't rush it.
re: Common issue
Yes, this is common. But while you're looking for aggression and physical factor, you need to remember that there's also technique, balance, breathing, self-awareness, environmental awareness, and a host of other things you can be working on - even with "wimpy" opponents. If your opponent is truly not pulling his or her weight, and it's not about skill (or lack therein), then your best action would be to work with your instructor. Your instructor, if he's any good, will likely know your opponents are wimpy and would have been trying to fix that. That being the case, don't bother the instructor with this, it's already being dealt with. If it's not the case (that the wimpy students are being worked on) then it means that the instructor isn't doing his job. As you are new there, it would take awhile for you to discern the difference.
It is also common for students to compare their instruction to what they see on YouTube. Don't buy into this!
It is also common for new students to be very gung-ho about their training, and to be disappointed because of expectations aren't met. Yet.