Is an algorithm that stitches together various algorithms "good enough" material for IEEE Trans?
"Stitching together" some existing algorithms is not necessarily bad, if the combination is both valuable and non-trivial. It can be argued that a lot of today's research in computer science is mostly stitching together ideas that have existed for a long time. Further, I am a huge opponent of the notion that it is somehow better / scientifically more valuable to come up with your own (almost always inferior) algorithms for well-known standard problems just so that one can claim to have a higher "novelty".

That being said, it is of course hard to answer your question without knowing the concrete work. As a rule of thumb, read through a number of back issues of your selected journal. If all of them seem to have a much broader contribution than what you have in mind, your idea may be too small (but don't let the impostor effect get you, either).