Welcome to the forum!
As far as I understand, that Pressed Steel filter is pretty old. (So is that Little Web Hut filter guide. Inkscape now has hundreds of filters which are installed with the program, and hundreds more which can be installed "manually".) In my opinion, that filter could be improved. Hhm....not sure if Lazur has made any metal filters.....see this message for links to his collections:
https://forum.inkscapecommunity.com/index.php?topic=329.msg2267#msg2267)
It's hard to know what might be causing the problems that you see, without being able to see your SVG file. Actually, it might also help if you could descirbe what you see as the problem.
What I see is that the top edge is sort of "cut off". That issue is known, and there's probably a way to fix it on your canvas, using the Filter Editor.
I also see some strange lines in the horizontal edges, but I'm not sure if the object to which the filter is applied might be causing that. If I make a similar object with Inkscape, I don't see exactly the same thing. But I might not have drawn the rectangle the same way you did.
Another thing to consider is whether these problems are display issues with Inkscape, which you would not see using a different viewer. For example, try exporting a PNG, and view with your system's default viewer. Or save the SVG file, and view it using your browser.
Beyond that, I would urge you not to "throw the baby out with the bath water". Just because you find one filter or one feature which isn't to your liking, doesn't mean the entire program is trash. If your use of Inkscape is limited to filters....well, then you might be disappointed with some of those very old filters. And if you're interested in creating your own filters, you'll really be disapppointed, since the current Filter Editor, is known to be in need of updating (indeed a process has already started to improve it).
But Inkscape is much more than just filters -- much, MUCH more! Anyway, let us know what you find with using different viewers. Also, if you want to share what type of graphics you typically like to draw, we might be able to suggest a more appropriate program, if it turns out Inkscape isn't the best for your needs.
Edit - Not that I'm speaking for Lazur. But if he has time, he might agree to make a better pressed steel filter for you?