No, no, no. "providing liquidity" is not a good thing unless liquidity is actually a problem almost everywhere people talk about this.
The "liquidity" provided by high-frequency traders in the stock market does not benefit anyone but themselves. For everyone else the difference between trading in minutes and hours (or even days) is near-meaningless. And they don't provide liquidity for seldom traded stocks.
And on the housing market they are not providing liquidity for the market in general. They are buying and then renting those properties out. Since they are all-cash offers they often trump "regular" buyers out of the market, even when offering the same price. Again, the only ones who benefit by this are those investors themselves.
These investors are one of the major forces pushing up the prices, the are part of the problem, not the solution.