It seems to me the biggest challenge for SE transitioning into ML is that ML is a very broad topic and people conflate a lot of roles together. From purely research based questions (backbones, optimizers, initializers etc), to more 'MLOps' like pipelining questions, which tend to fall into the classical engineering / dev ops buckets. So the real question is what type of ML do you want to do?

If you're looking to land a job at FAIR / Deepmind or Google Brain/ Nvidia Research as a researcher or ML scientist the expectations of knowledge are very different than 'data science'. These are research lab groups, that work on pushing the state of the art forward. They are also supported by great engineers, building awesome tools that improve ML research. So transitioning into this sort of role requires more than doing Kaggle competitions, it requires developing an intuition for the respective ML subfield / and trying new things and usually failing. i.e. this is a research role and will require a lot of study and learning

If on the other hand you are looking for datascience / take model and build pipeline to run AI, or perform hyper param sweeps or simply modify some model code, then on I would say that is much more engineering than research ML. This has a much lower barrier to entry coming from engineering and could be a good stepping stone to a transition into pure ML research.

On a more general note to consider when thinking of transitioning to ML is that these systems are probabilistic in nature vs purely deterministic as they are in more general software systems. People (ie humans) are bad at wrapping their heads around distributional processes - you can see this in all fields that deal with them (Quantum vs Classical Physics, Biological Systems etc).

In general I guess what I have seen is when engineers try to dip their toes into ML, what's required is a mindset shift in how to approach problems. Once that happens the depth of that shift determines the type of role with ML you wish to pursue.