I bake almost everyday, sometimes I am very happy with my baking results and sometimes I am not and when I don't like it, I think it's me as a beginner, I might have done something wrong or not quite right. After 15/16 months of baking at home, I feel like something is wrong with the oven I use. I use the upper level to get better results and I even bought a new baking tray. It actually made the result better but the result did not meet my expectations. I would pay for a better oven if it makes a very big difference. How important is oven in getting great baking results?
15/16 months and now you're questioning the oven. A new oven with new features is ALWAYS a good thing, but you will still need to adapt to it, and it's not going to be perfect. I've baked in a variety of commercial ovens and home ovens and each has its issues. It's easy to say "of course" steam, or "of course" convection, or gas or electric or whatever. In real world practice, we bakers just adapt and get on with it.
For reliable baking you need to know what your oven is doing. If the internal temperature fluctuates wildly, you're dead in the water: replace it. If it's fairly stable, spend some time learning it. Get a decent oven thermometer; set the oven's temperature control to, say, 350 degrees (F) and let it settle; check what the oven thermometer says. Then work through various other temperatures, so that you know what you need to set the oven's temperature control to in order to get the internal temperature that you want. For example, to cook something at 350 with my oven I set the control to 325; to cook at 450 I set it to 420.
In terms of typical baked goods, radiant heat is radiant heat. Different ovens are not going to provide you with different heat. However...a couple of things to consider: Most consumer ovens are fairly inaccurate in terms of actual temperature vs. temp. on the dial. Get an oven thermometer and keep it in your oven so that you know how "off" yours is, and you can compensate. Secondly, convection vs. non convection can make a difference. A convection fan moves air in the oven, providing you with, essentially, a higher temperature. However, you will likely have to rotate your product for even browning. The only place where I could see the actual mechanics of the oven making a difference is in bread baking. Most artisan, professional bread bakers use ovens that allow the injection of steam. Bottom line given your question: Start by checking your oven temperature.
The best advice here is the recommendation of an oven thermometer. I suddenly had issues with a fairly new stove that had baked superbly. Many disasters until I did two things: store my flour, sugar and other dry baking goods in the refrigerator (my area is exceptionally humid these days) and purchase a thermometer. Turns out my oven was 25 degrees hotter than it read on the dial. And my dry goods were storing moisture so it weighed more in mixing but when the moisture baked out it was flat and cooked unevenly. Also, be sure your baking racks are placed in the center of the oven and your goods are on the denter of the rack.