The hashing rate is not directly relevant. That's roughly proportional to the daily dollar value of the reward times the efficiency of the leading mining hardware. The latter has gone up many orders of magnitude over the years.

> block rewards have been diminishing regularly

That's exactly what the poster you're replying to argued; the BTC denominated block subsidy halves every 4 years, and so without a corresponding doubling in price, the bitcoin security budget keeps diminishing, at least until tx fees start to dominate the subsidy.