If the trainer is too easy, you can make it hard. Do some intervals. We had a rainy season years ago here in California, I know, hard to believe. SO I got a trainer that year.
I read up on some interval trainer (pre Zwift years). I would do a one minute biggest gear interval. Relax while spinning for 3 minutes to recover. Then do a 100+ cadence for 1 minute. Repeat as many times as possible. I would warm up for 5 to 10 minutes first. But once you start the intervals, it does not last too long.
Sometimes I would throw in a 5 minute hard effort in a big gear to mix it up.
I did place a personal fan on a table in front of me and crank up the headphones with some AC/DC. 😄 On a mat if indoors because you are going to DRIP!
But yes, some people make it too easy. I remember years ago, bike in bikejournaldotcomm days, some lady on a forum said she would do a 20 MPH average speed on the trainer while reading a book in front of her fireplace and had mega miles logged. But her outdoor rides were averaging 14 MPH over 20 miles. So be realistic. :p