I've created two web series (most recently, The Canadians, a parody of FX's The Americans, nominated for two IAWTV awards) and been heavily involved at the EP/writer level of a third (L.A. Beer). Making a web series is a great way to learn how to showrun, to collaborate with multiple directors, to select a crew, to do post-production. It's great training. It also relaxes you internally; you know that no matter what, you can make and finish something for the screen, and make it serialized--you don't need millions of dollars. Every TV writer should do it at least once.
But no, it's not helpful to pitch for multiple reasons:
1) Financially, the industry only cares about webseries if you get well over 100,000 views, which is very, very hard to do.
2) People's minds decorate your sets with multi-million dollar budgets. When you shoot something, you don't have that money, so it can actually hurt you.
3) Web series are structurally different from TV in fundamental ways; you need to write complete episodes that happen in 3 minutes, not 30 or 60, and you need to really write to the locations you have, which often is someone's apartment or office. It's restrictive in a way TV writing isn't.
The rare, outlier web series that do stand out are ones that had a completely unique voice (Broad City, Awkward Black Girl), often an underserved audience, and were actually made -as web series- as their final goal, not as pitch demonstrations.
That said, I've met some great people I'm still really good friends with from my webseries, people I'll be hiring if I'm lucky enough to create my own TV show.
Yep, Amazon prime. I only watched one thought.