A less permanent change to your current skates, if it is the heel that is loose, would be to use a heel cup. There are many different types and shapes available, and many are cheap. Alternately, you could also play with adhesive foam or tape, placed inside the boot in the places that feel loose against your foot, until you feel the fit is perfect. Some skate techs know how to do these things, and some don't, but with a little experimentation, you can maybe do it yourself if you are patient.
I should have clarified that I am one of the relatively few people here who think you can do a lot of adjustments by yourself, if you spend a little time and patience. I think most skaters with equipment related issues (including much more expert skaters than me) eventually find an expert fitter/skate tech who does what they want, and keep buying new equipment until they find something that works for them. Or give up.
But to me, it just seems like basic geometry and intuitive physics. I don't think there is anything magical about it. E.g., you can fill space, and to some extent stretch materials to make more space. Equipment related balance and control are created by relatively simple principles and changes too. Skate sharpening isn't magic either. I love how to figure out how to do those things for myself, using basic equipment.
(Even so, sometimes you do need new or different equipment. I'm going through that now, and finally acknowledging I should have done that a long time ago.)
BTW, there is "magic" in medicine and in a really good teacher (such as a really good skating coach) whose methods and solutions happen to click with your individual body, mind and learning style. Meaning it isn't possible to learn everything they have learned, unless you have a knack for it and spend enormous amounts of time learning it under the tutelage of existing experts.
I don't choose to let that scare me when it appears that I just need to fill or make space, or shift points of balance in my equipment. Plus I like figuring things out at least as much as I like skating.
But if you find a good fitter & skate tech who can help you do it, that may be a quicker (though maybe not cheaper) path to skating nirvana.
