I think it is wrong, especially after I listened for one hour to Boris Milanov yesterday on wiwigbloggs youtube channel.
The songwriters were forced to submit their songs by 9th of March, which is not the same thing as releasing them. They wereonly released to the EBU Eurovision channel. 9th of March was a date when rumours already had it that ESC 2020 might be postponed or canceled. So, for countries that haven't submitted their songs yet as of this date, such as Bulgaria or Russia, it was a perfect trap.
Furthermore, the pre-Eurovision audience is small. Too small to make an impact. First of all, the performances are voted for and not the music videos. No one will see a performance. 5-10% of televoters already know all the songs. There is no harm in allowing the songs to be carried forward to 2021.
Songwriters for Eurovision 2020 songs don't see any royalties, except for their songs chart without Eurovision. Singers get a lifeline for 2021, songwriters don't. It's very unfair.
But I can also understand people who say that a mix of old and new songs is strange.
Who would these people be? Only die-hard Eurofans and blogosphere. The vast majority of viewers at home and juries would not care. So, I cannot really grasp this notion.