It is almost certainly true that it has always happened far more than was documented. There may be limited historical data about that kind of violence, but there IS good data on changes in law enforcement policy, including the militarization of police forces, and changes in the way new officers are trained.
SWAT interventions have increased from 3000 cases nationwide in 1980, to over 50,0000 cases in 2012, and the criteria for their use has broadened to a frightening degree - so much so that they are now used in simple warrant services where no armed or organized resistance is expected. No knock warrants have gone up a smaller, but similarly frightening amount, and the paramilitary units are far more heavily armed and equipped than ever before.
Officer training has also now shifted from a focus on “de-escalating”, with force as a final alternative, to an approach much more tolerant of non-lethal force and with relaxed restrictions on the escalation to lethal force.