Despite the grinding, slow start, it does seem that 2021 is the year in which the roll-out of addressable advertising is making some notable progress. CBS has announced plans to make addressable advertising available across its broadcast network in the latter half of this year, with smart TV inventory getting a look in, too. This follows ViacomCBS delivering the first ever addressable ad within a live national broadcast in January to select Dish Media set tops. Now the network wants advertisers to know that the flood gates are open, although we imagine the slow trickling momentum will persist for some time. The new addressable inventory will be carved out from the space where CBS traditionally runs its promotional material for…