Some are, some aren't. I happily got the NES and SNES retro consoles when they came out and I play them on a modern TV or monitor. I don't care about the CRT scanlines and artifacting. (I do care about a CRT's lagless instant response time, which is an issue for some games. I do have HDMI monitors with as low lag time as you can get.)

The old Atari consoles are common, but it's hit and miss as to whether they work well or at all, particularly the power supply and also the controllers. It's reasonable to spend a few bucks on some modern hardware if you want. I probably wouldn't play Atari games quite enough to justify it myself.