It sounds like you spent most of your time at Disney and otherwise in Tokyo, though. That's not representative of Japan. Though, even in Tokyo, you'll eventually run into small restaurants and shops that don't want credit cards (or at least not foreign ones). A few years ago, you'd still run into some cash-only taxis, too, but I think they all tried to fix that for the Olympics.We have been using our credit cards everywhere with zero issues (other than in the Disney app - in person was fine)
For Suica, I have an iPhone so added the transit pass on there and just used Mastercard via Apple Pay to load it. I used ¥10,000 over two weeks (we stayed at TDR the first 4 nights and last 5 nights, so separately bought the 4 day monorail pass for ¥1500 (that was cash only)
I brought ¥50,000 but would have done fine with ¥10,000 …very rare did I encounter cash only.