It would be very interesting to ask a JW this question. Who are these scriptures talking about? -- who puts these heavy loads upon their flock?
And the j-dub would answer something like, "Why, the clergy of Christendom, of course." (an aside, have you ever noticed how often JWs and the publications preface or end a sentence with '... of course...'??)
And then you would ask, "And what are these heavy loads and burdens they put upon their flock..?"
Yes, I would love to ask those questions.....
(... and I used to wonder too, about Jesus' words about his load being light, and that we would find refreshment! It sure didn't feel that way!!)