The original Postman Pat, Fireman Sam, Thomas the Tank Engine etc are OK as they are fairly slow paced and charming. They do have some dated aspects like stereotyping of characters, Thomas is quite weird in parts, although TBH small children don't really notice. I'd steer clear of the more modern CGI versions, as they are a bit soulless and they move very fast.
What you tend to find with modern TV is that it is constantly moving and cutting between scenes, zooming in and out. That's because it's more engaging to toddlers, but it actually has almost hypnotic properties which is not good for them.
I actually really like Peppa Pig - it's quirky and there are adult-level jokes in there. Maybe watch it yourself and decide.
I hate paw patrol - it's lazy, fast-paced and stuck in the 80s with its one girl character that is smaller and weaker than all the "real" boy character 
Stay away from youtube in general because a lot of the "episodes" of programmes are just loads of clips mashed together so the narrative never makes any sense, it will also automatically funnel you towards the bad (Blippi, Cocomelon), the worse (random children and adults putting on a nauseating voice "playing with" (opening, looking at, covering in paint) literal mountains of plastic toys), or the fucking weird/creepy - computer generated weirdly terrifying loops of animated items being dunked into different colours or crushed 
I'd stick with iPlayer, the CBeebies channel on TV, DVDs, subscription services (netflix, disney) that you control, or downloaded bought programmes that you control.