Block space needs to be limited to ensure bitcoin's long term survival.

Given that the block subsidy is halving every 4 years, it will not be long before the subsidy alone is negligible and certainly not enough to support even a fraction of the current hashrate. At that point, fees have to be sufficient to take over. For fees to be sufficient, block space has to be limited and there needs to be a full mempool and a competitive fee market. If we increase block size so everything can confirm at 1 sat/vbyte, then even for a (let's say) 16 MvB block you are still only talking about fees of 0.16 BTC.

If you want everything to confirm in the next block at tiny fees, then you need some other mechanism to pay miners once the subsidy is insufficient. That means either lifting the cap of 21 million and having constant inflation, or some other mining incentive like merged mining.