I haven't been in that line of business for 10+ years, so my understand and reference is also a bit out of date.

Retargeting did very little. Ads helps in some cases, but rarely generic ads, it had to be extremely targeted, which was normally done by manually buying ad space with certain TV programs or in specific locations. The big ones for us was price comparison sites, if we could get on HotUKDeals we'd have a great week, but in particular Google Shopping did made a big difference.