If you have a machine and it is working well, straight stitch and zigzag is all that is necessary. At least one automatic buttonhole is nice/convenient to have, but beautiful high quality clothing can be made without it.
If the machine is too cumbersome, why not keep an eye out for something used? There's a Brother machine being offered here locally for $50. Approx. $150 -$175 to buy an equivalent machine now. Seller states "it's been taken out of the box once - but never used." My sister has a machine that would meet that description had her daughter and I not borrowed it. This way, you can try out something different and decide if IDT or something else is important to you, before buying something else you're not satisfied with.
All that is important to me is a good stitch, reliability, one quick buttonhole, and a stretch stitch - but I could live without the stretch stitch if I had to.
My serger sat unused in its box for almost 20 years. Received as a gift, I didn' t use it until I started sewing a few knits.
So long as a machine is working properly, the quality of clothing produced is 100% dependent on the skills of the sewist - not on the type of machine used.
Is your machine working properly? Does it hold tension correctly? What is it that you don't like about it?
There's a woman named Evelyn Wood on YouTube, I think she's out of NZ, that has extremely good videos about sewing. She also has an online school. Check out her free YT videos and see if maybe taking classes might be of assistance. There isn't a sewing machine made that will take the place of skill and experience - and those require time and practice to develop.