TDA2004 was never a good device. It was designed to go in low cost record players and tape recorders. I think it went out of production in 1996!
The specifications shown are "Absolute maximum ratings", that means if you exceed those figures the device will be damaged. You really need the "Electrical Characteristics" table in the data sheet to see what it can reliably produce. In particular look at the distortion vs. output power graphs, you will see that despite it's size it produces serious distortion from about 2W upwards.
There are MUCH better devices these days that produce higher power, lower distortion and are far more power efficient.
Brian.