The core of the claim is this line, talking about the ActBlue fundraiser platform:
But by going to the “Expenditures,” page, you will find that Top Recipients are exclusive, Democratic candidates and their campaigns.
That is to be expected, as ActBlue is a left-leaning platform specifically to "enable Democrats, progressive groups, and left-leaning nonprofits to raise money on the Internet by providing them with online fundraising software". Complaining about such a platform having Democratic campaigns and candidates as Top Recipients is like complaining that WinRed has mostly Republican campaigns and candidates as Top Recipients.
Donations go to the campaign indicated, unless...
In the event that a campaign or committee (a) fails for 60 days to cash a check from ActBlue which includes your contribution (after ActBlue makes repeated attempts to work with the campaign to ensure all checks are cashed), or (b) affirmatively refuses a contribution earmarked through ActBlue, your contribution will be re-designated as a contribution to ActBlue. Contributions to social welfare organizations which are similarly not cashed or affirmatively refused will be kept by ActBlue and used generally to support its social welfare activities. Contributions to charitable organizations which are not cashed or affirmatively refused will go to ActBlue Charities.
So even if Black Lives Matter would not cash in on their donations, that money would go to ActBlue, not to some Democratic candidate.
Looking at some lines at the actual article from thegatewaypundit.com, a far-right news and opinion website known for publishing falsehoods and spreading hoaxes:
Donations go directly to ActBlue...
False, see above. ActBlue is not the recipient, they are the service provider.
(Do all the individuals around the world know that when they donate to Black Lives Matter, that they are also helping to fund an organization that supports the Democratic Party?)
Every organization is leaning one way or the other. I'd suspect that somebody willing to donate for BLM will be neither surprised nor dismayed by the fact that the funds get processed by a Democrat-leaning service provider, or that they will take a percentage of the donations as payment for those services.
This is just another corrupt wing of the Democratic Party.
It simply does not follow from the "evidence" given, and again I'd like to point to WinRed, which does exactly the same for right-leaning campaigns. Which then, by the same token, would have to be considered "just another corrupt wing of the Republican Party".