Stepping on soil can compact it, yes, especially when freshly-tilled or saturated with rain. Since you need to access the garden to weed, you could try using a wooden plank/board or two to stand/walk on to more evenly distribute your weight to minimize compression. If there are particular pathways next to or through the garden where you won't be planting, using a mulch (such as fresh wood chips) on just that area can also reduce compaction from foot traffic while helping to keep that walkway weed-free and improving the soil underneath over time.

While roto-tilling can make breaking-up compacted soils easier, it also happens to damage soil structure, disrupting the natural processes that help bind soil particles and keep them from compacting again as easily. Instead, loosening the soil as needed with a garden fork is indeed a better technique. Instead of turning soil over, using it inserted vertically into the ground and wiggling/rocking it back-and-forth can help work-in amendments like compost (purchased or home-made) while keeping as much soil structure intact as possible. Annual amending with a topdressing and forking-in of compost can rejuvenate the soil structure over time.

If compacted soils are too challenging or deteriorated to work, they can be used as an underlayer for raised beds built over top of them, which can be filled with a looser soil. If the original soil is loosened first with a garden fork, roots may very well be able to grow down into this denser soil once they reach the bottom of the raised bed. Here is some raised bed info. if that is a preferable option: https://extension.umd.edu/hgic/topics/soil-fill-raised-beds

Miri