From the top of my head, I welcome additions to the list:

Technology

• Long read sequencing PacBio and Nanopore has greatly improved.
• Consensus calling sequencing runs with PacBio can give you near-perfect over 2-3KB long reads that allow you to assemble small genomes with ease.

Concepts

• RNA-Seq Velocity: https://pubmed.ncbi.nlm.nih.gov/30089906/

Improved tooling

• Minimap2: https://academic.oup.com/bioinformatics/article/34/18/3094/4994778
• Kraken2: https://genomebiology.biomedcentral.com/articles/10.1186/s13059-019-1891-0
• Salmon: https://combine-lab.github.io/salmon/

Are you primarily a biologist or a computer scientist? If latter you should be able to catch up with whatever you need on the job even if you missed it. If former then answer would be "depends". If you had enough expertise with topics that were around in 2016 then those would still be useful. Things that have taken off since 2016 are alignment free expression quantification, single cell + (any technique that was used for "bulk" samples) and Spatial transcriptomics that you will need to catch up on.