Re: Dead end?
They say "practice makes perfect" but others say "practice makes permanent".
If you practice "good" form/basics/movement priniciples/suburi/etc., you will build a good foundation on which to base a long healthy aikido "career".
If you shut your mind off and stop paying attention to what you're doing in your repeated practice, you may be practicing "bad" movement patterns which will stay with you through your "career".
Better to be "mindful" - in some circles this is called "deliberate practice" rather than anything mystical - and pay attention to what you're doing while you learn things.
In the sport I coach, some of the conventional wisdom is that you spend the first year learning the basic motions and how to be in control, after which you can start working on being fast. As another has mentioned, if you want fitness, go running (or swimming) and throw some steel around. The thing about starting slowly with aikido is that unless you've come to aikido with a very solid fitness background, all of the movements are novel to you and to your "core" - strength and stability - the little muscles surrounding your spine which provide support for all your movements. Your brain needs to learn to control all the muscles, joints, ligaments, tendons so that you can be strong and stable without being stiff and tight. I THINK this is the base learning that some of the "IS/IT" folks talk about, but whether or not, these learning processes take time, repetition, and (again) deliberate practice.
Sounds like your basic practice is what's going to form a good base. It's good that you enjoy the training - keep at it.
Patience... (early in the movie - "The Challenge" with Scott Glenn, 1982 IIRC - Glenn asks his little friend what he learns from having seven brothers - Patience - you learn patience...)