Without a doubt, secure access is our biggest improvement.
My buddy bought my land originally in 2013, then I bought half from him in 2018. I've been able to hunt it since he bought it, and my contribution until I bought was I did most the habitat work. Today we both share in the work of both parcels and hunt both.
Anyway, he closed in early October that year. Closing with season already open, there was no improvements or stands hung. Property was a third each of ag, park effect timber and swamp and we experienced some pretty spectacular hunting that season. Well, until the crops came down and pressure built up at least.
He then hired a big name consultant who formulated a plan and we went to work implementing. It was a checker board of food plots and bedding areas with stands scattered throughout. We'd have a few good sits every year (killed a couple good bucks) and the property would just turn off. The more we did, it seemed the worse the hunting got. The plan had a major flaw, which I identified right from the get go, and that was secure hunter access.
When I purchased in, it was with the understanding that the consultants plan needed to go. With now a few years of hunting frustration, my buddy was happy to welcome change. A habitat pioneer friend of mine always would tell me his goal in setting up his property was to never let deer see, hear or smell him. So I formulated a new plan with those goals in mind. The center of the property was designated sanctuary and the major food plots moved to areas where natural topography screen our movements. We don't hunt food except from gun blinds we can get in/out cleanly without alerting deer in the plot. We rarely hunt more than 30 yards from the property line leaving the vast majority of the property to the deer. It's been a dramatic improvement. We are seeing, passing, and killing more and bigger bucks than before by a wide margin with relatively the same quality/quantity of food and cover.