"They have no vision. What they've evolved into is a company that does [arbitrage] on acquisitions. It's stock buybacks. Who is IBM anymore?" Cuban asked in a "Squawk Box" interview.
In response to Cuban's comments, IBM said via email to CNBC: "When it comes to investing in the business and returning money to shareholders, IBM has done both."
Cuban said the old Big Blue used to have recognizable products.
"They specialize in financial engineering," he said. "To me, that's not a future." He noted that Warren Buffett is a big IBM investor, and said he's a big fan of Buffett, but not of IBM.
In its response to Cuban, the company said: "IBM will accelerate our growth strategy, creating a dedicated cloud business and specialized units to serve industries and professions being transformed by data and analytics. IBM will also continue to return money to shareholders, in addition to maintaining our commitment to R&D and to invest in our business. It is all part of our commitment to delivering higher value to our clients."
Shares of IBM has been under heavy pressure this week after its big earnings miss on Monday. It moved higher on Wednesday. (For the latest stock price, click here.)
Cuban, who made his fortune as a tech entrepreneur and owns the NBA's Dallas Mavericks, also explained why he bought Netflix stock on last week's dip—50,000 shares worth after the streaming video service had fallen about 20 percent in five sessions. He said he also sold put options.
Netflix is a disruptive company that seems to get first dibs on a lot of the original television content being created, said Cuba, who's also chairman of cable network AXS TV and a co-host of CNBC's "Shark Tank."
Last week, Cuban tweeted:
He said he is not investing with rose-colored glasses: "There's never been a high-flying tech company that hasn't hit a bump in the road, but they're smart. They have a lot of momentum."
If there's a concern, and there always is," he warned, "they have to replenish all that great content." Netflix original shows like "House of Cards" and "Orange is the New Black" are great, but buying more shows to bump subscribers is tough to do, he added.
Following better-than-expected earnings and revenue from Yahoo on Tuesday, Cuban told CNBC he's rooting for the company to succeed.
"They have a platform that's incredible. They added Tumblr, which is an incredible platform. Tumblr continues to grow," said Cuban, who added that he was encouraged by Yahoo's $200 million in third quarter mobile revenue, which was 17 percent of total sales.
"I hoping [CEO Marissa Mayer] takes one or two pages from Google, one or two pages from Facebook because Facebook is doing a lot of really great things. Yahoo could step into the conversation," Cuban said. Mayer was a top Google executive before joining Yahoo.
All that said, Cuban said he would not buy Yahoo shares because too much of the company's value is wrapped up in its investment in Alibaba, whose IPO last month was the biggest ever.
Cuban also spoke about Tesla Motors. On Tuesday, Michigan has become the fifth state to prevent electric car maker from selling directly to consumers.
"I'm not a big fan of that," Cuban said.
Tesla, which has challenged some of the long-held conventions of auto industry, wants to set up its own stores rather than to sell through a franchised dealer network.
"It just goes to the heart of the whole approach to convincing politicians to do something for you. It really sends a bad message when lobbyists can convince a governor and a legislature to do their bidding for them," Cuban said.
—Wire services contributed to this report.