Choir-Sung Commercial Jingles. During The Seventies and The Eighties, it was very common for commercial jingles to be sung by a choir of (usually middle or senior aged) men and women. This quickly changed once the MTV Generation came of age and the corresponding network began to seriously influence grownup advertising (it was already influencing children's advertising since about the late 1980s). Before long, choir-sung jingles were perceived as outdated and un-hip. Today, while such jingles are occasionally used in local business advertisements, most mainstream ones are performed by professional rock or pop musicians rather than choirs. On those rare occasions when you'll hear a choral tune in mass-market advertising, it will be done sarcastically.
Cigarette ads. They were banned in 1970.
Early on, television shows would have the ads contiguous with the show ("This portion of [name of show] brought to you by [product]", read by The Announcer). This format was especially common on Game Shows, which would often have the name of the product displayed somewhere on-set to boot. Over time, commercials took on the format that they have now.
Advertisements for home appliances, such as dishwashers and vacuum cleaners, fell by the wayside during the late-90's. This could probably be attributed to the internet making product reviews much more accessible. Meaning potential appliance buyers can now simply go on the internet and look up professional/customer reviews for whatever appliances they are planning to buy rather than relying on television advertisements. If a home appliance is advertised, it will usually just be through an infomercial.
Another possible reason for this is that home appliances were generally marketed towards housewives and stay-at-home mothers during daytime television. Today, with more women going into the workplace, this market has significantly diminished.
Cartoon show-tie in toyline commercials. Ignoring the fact that the shows themselves were akin to 30-minute commercials for the toyline. There are now no cartoon shows based on toylines. They haven't been seen since the early 90s. The FCC has issued strict government regulations on advertising aimed towards children and this was one of the first things to go.
GEICO ads were once regarded as funny and creative, and often reached Memetic Mutation status. Now the company is seen as a joke that no-one can take seriously and the commercials are seen as annoying and repetitive, with nearly all their new characters becoming scrappies.
Ditto to Ditech. In the early-2000's, their commercials with "Ned The Incompetent Loan Officer" were seen as hilarious and made the phrase "Lost another loan to Ditech" a Memetic Mutation. Today, the company is seen as a subpar lending firm.