Crystal Palace already had one trophy, and even if they end the season without achieving anything now, no one will say they end the season trophyless, and the Community Shield is a well-known title, so I don't count it as preseason matches as you said, and Liverpool put in their best effort in the match, it's just that Crystal Palace didn't just give up on the pressure they received, like they did against Manchester City in FA cup.
I do not think Liverpool gave their best in this match. I definitely expected a better performance from Liverpool. It wasn't a friendly match. The Community Shield is definitely an important trophy. But Crystal Palace's performance was better than Liverpool's in this match. In the whole match, Palace players had a total of 14 shots, while Liverpool players had 12 shots. Especially I would say that we didn't see a better performance from Salah in this match. He could not play well for 90 minutes, at the same time Salah missed the first penalty shot. Fans definitely expect a better performance from an experienced player like Salah.