Need to activate scapula and the lats. When doing bench initiate the movement from the scapula ,pulling them down and back, not from the weight in your hand. Sounds counterintuitive but doing so takes the arms and front delts out of the movement. Before you know it your chest will start doing the lions share of the load.
Even if your not feeling it in the chest at first get a training partner to press their finger into your pecs as you perform the movement. As long as its contracting you can be assured your getting stimulation.
Over the years a lot has been written about mind/muscle connection. A lot of it is bad because it only focuses on concentrating the stimulus on the target muscle. Any exercise whether its an isolation or compound, the target muscle is still only one part of a chain. You still need to pay attention to your posture, positioning, joint stability.
In a bench press and you are naturally arm/delt dominant if you focus on feeling it only in your pecs, you can bet your shouders will become unstable. After time, doing it this way leads to a hunched over upper back, sore neck and impingement in your shoulders.
Get the scaps,lats doing their fair share creates a stable base, and allows the pecs to increase their workload.
When doing this its a good idea to lessen the weight a bit so strength is not the primary focus at least until your technique improves, more of a bodybuilding rep range 8-12.Concentrate on the negative portion of the rep. After a month or so you can go back to 5/3/1.