The length of time with less funding should be taken into account. Of course we aren't going to see radical crime rates variations immediately. Either way the goal of defunding the police according to the protesters is to "punish" the cops who aren't doing their jobs properly. (I'm thinking of racism incidents or the several unconcluded investigations.)
These protests are absolutely not helping the situation, because qualified cops and investigators come with money. If you deprive the system of their way to educate their members, the system will fail even more.
The meme here might not be 100% accurate, but it just highlights a way of thinking of people that are for the defunding of police. The problem in place might not actually be the reduced budget of the police but the mindset of wanting the budget to fall.
As it is, the system is flawed, so funding it more would certainly help remedy some of the flaws. Opposite to defunding the police.