Some highly experienced and very competent systems engineers when discussing Model-Based Systems Engineering (MBSE) sometimes overlook something that those of us who are very experienced with SysML tools like MagicDraw/Cameo are increasingly aware of. SysML tools have enormous power for many Model-Based Engineering (MBE) tasks that have nothing, at all, to do with formal Systems Engineering!
Most dedicated older Systems Engineering tools are primarily used for formal Systems Engineering; modern SysML-based MBSE tools are useful for many additional things, including just graphical Model-Based Engineering (MBE).
For example, there are hundreds of examples on this Webel IT Australia site of modelling existing systems and human language descriptions of them using the Webel Parsing Analysis recipe for SysML® or just freestyle SysML modelling of devices, which useful SysML models do not employ any classic functional analysis breakdown, at all. Zip, nada, null. Because it's simply not relevant to those tasks!
SysML-based tools such as MagicDraw/Cameo are MASSIVELY better for graphical modelling for many tasks in the hands of experienced users than, say, PowerPoint or Visio, which are not Single Source of Truth (SSOT) tools.
For example, here's a link to a large IBD of an Arduino board:
It's part of a wider tutorial slide trail showing a recipe for modelling electronics using port-based engineering and flows in SysML:
Another example: SysML Parametrics are extremely powerful for breaking down complex systems of equations graphically and for understanding causality and dependencies. They have standalone value without necessarily any integration with a wider formal Systems Engineering model or methodology.
You can learn a lot about any device modelling it in SysML, including systems that already exist. Maybe their original designers did indeed use formal systems engineering, but that's not what you are doing, you are just modelling stuff in SysML, maybe just for fun or to learn SysML.
If you enjoy and have benefit from just using the graphical modelling capabilities of SysML in your tool, go for it. And don't feel obliged to always use formal Systems Engineering approaches for every task.