Welcome!
Apprenticeships are interesting since they involve two separate components - the hands-on at work, while the in-school portion tends to be more theory, but also building upon the skills that the student was expected to have worked on over the past months or year.
In an ideal world, the employer is understanding and supportive of the apprentice's needs - to ensure that they have exposure to a variety of things, both hands-on and as an observer, to encourage the apprentice to apply for the in-school portion only when they are ready, and to allow the apprentice to have the time off to attend. Basically, the employer is supposed to be a mentor.
Unfortunately, it's not unusual for this not to be the case.
Sometimes the employer doesn't fully understand their role in training and so doesn't provide enough support and/or rotation through different skill sets.
Sometimes the employer is shorthanded and doesn't have the ability to provide the support and/or rotation.
Sometimes the employer sees the apprentice as cheap labour and doesn't care about helping them advance to the next level.
etc etc.
In cases where your employer sponsor isn't really working well for you, then that's where, as hard as it may be, you'd want to consider looking for a new one. Ultimately, you have to look out for you first.
From what you describe, it seems like the trade might be perfectly okay for you - it's just a matter of getting the right support.
In my work doing job/career support, one thing that I often stress is that people often ask about the right job, the right company, or the right industry. But quite often, it's about having the right boss.
Best wishes and of course happy to answer any questions.