Like almost everything in life, the answer to that question depends on the context.
A remaster or remake can be good if it serves to raise funds for the studio, to return attention to a franchise that has lost its audience, or to serve as training for a new studio.
But they can be bad when they become substitutes for new games, create a culture of harmful and reactionary nostalgia or occupy highly trained studios.
A well-positioned remaster in terms of time, space, resources and prices can be good. I mention the example of Crash Bandicoot: a studio that grew after launch, 3 games for 40 and brought a good mindset to the franchise.
A badly positioned remaster is that of Pokémon: it took the time of a major producer, the game was already accessible in two versions, the price was full and there was no lack of content in the franchise.
