Landscapes - when to move away from kit lenses

I have been eyeing the Tamron 15-30mm f/2.8 Di VC USD Lens for landscapes to use with my Nikon DSLR. I know the price of the lens is good relative to the quality, but I still balk at the cost because I would rather spend that money on a trip. However, for landscapes, I've now been shooting with a kit lens (16-50mm) on my Sony mirrorless camera for a year. The images seem soft to me, even when I use a tripod - but I'm not sure if that's my technique or the lens.

So, my question is, would a beginner hobbyist really even notice a difference in quality between kit and higher end lenses? Is the difference pretty significant? Or should I spend more time on technique and further my skills in editing?

Both images below are handheld with the kit lens.