1) If Hawkeye had a Season 2, Renner would have been limited to a mentor role, both because Kate is now the lead and because Renner is still physically limited - why would you pay a supporting actor lead actor rates?
2) There's definitely some severe penny-pinching going on at D+. Think about it, the only unaired Marvel shows were announced, if not actually filmed, years ago - Ironheart, Wonder Man, Zombies cartoon, Wakanda cartoon. Hell, that's not just Marvel - Star Wars only has more cartoons that were also started years ago and the relatively cheap cast of the (final) second season of Ahsoka. (I can't imagine why anyone would pay for D+ if it wasn't baked into another service you have.)
Is it 'disrespectful'? Sure. But it makes perfect business sense.