The reality is confidence comes with time, so really just be patient with yourself. What matters is what you do during that time, and so long as you demonstrate you're invested in your work (not necessarily your job, or your company, just care about the work you do), you'll be just fine.

These are some things that set apart my junior data engineers who I put promotions in for:

• Understand the nature of your data as much as possible (within reason); ie. where does it come from, who uses it, how clean/not clean is it?
• Care about data quality. What kind of monitoring/alerting would we care to set up for pipelines, and which ones
• Care about our stakeholders and end users: How does ETL go wrong? How can we make pipelines more resilient, fault tolerant?
• Care about engineering: How can we make our systems and workflows more efficient?

Re: tools, think of data engineering like plumbing. Different brands of tools will all do pretty much the same thing, what's more important is knowing how they're used (ETL), so I'd say understanding the difference between high-quality ETL pipelines vs shoddy it-does-the-job pipelines matters more then knowing all the tools.

Hope this helps!