More so a factor of time I believe.
It takes practice getting the results you want.
I recommend trying segmented work, be creative, try scalloping different ways, try gluing up a stack of off cuts and laminates and cutting on a blank on different angles.
The closed end is a good way to improve skills.
and as mentioned, turning different objects is always a good idea.
Try some of the more challenging materials to work on tool control. Best materials I have found are pine and other soft white woods, it's everywhere and with its soft open grain can be very challenging to tool. I know a lot of people learned a lot of lessons in last years pine PITH. Aluminum rod will definitely teach correct tooling technique as well if it's chattering, you're not holding the tool correctly, if little chips are coming off instead of ribbons, your tool isn't sharp enough and you're holding it wrong. With sharp tools, aluminum rod is easily turned on a wood lathe.
Try making your own tooling out of delrin, brass, or aluminum rod instead of buying, this improves your skills and reduces your tooling costs. If you can make a set of delrin finish bushings, you can make a section for a fountain pen or rollerball. If you can make some closed end mandrels out of brass or aluminum, you can do most any part of pen making.
Please share your tooling situation as well, chucks, mandrels, turning tools, taps and dies, lathe type, etc. that you already have. Some tools you're going to end up spending on if if not already available, but there are lower cost paths in many cases. Example is the triple start taps and dies. If you're new to kitless, don't plunk down big bucks there. Buy the off the shelf taps and dies in sizes recommended in other threads for lower cost to get started and make sure you understand the basics and like what you are doing before spending big. Instead of buying closed end mandrels, try making your own, it will teach you precision and and how to use that new die.
Just my 2 cents on the subject.