Would you still recommend investors buy and hold REITs given that a lot of the REITs are slashing their dividends? Or should we buy and sell to take advantage of the market volatility?

Depends on your mindset and investment strategy.

Some REITs are undervalued when you compare their stock price vs the assets that the company has. And over time, the price should recover.

Buying and selling incur transaction costs. So the consideration is not purely based on the stock price. If the price difference can cover the transaction costs plus giving you a profit, it could be worthwhile.