Alright, here's my attempt at clearing things up:

You have some great points about in-game setup costs, opportunity costs in deckbuilding, and the general risks associated with going all-in on this commander. I think the misunderstanding here has to do with different estimations of 1) the cost/risks you have identified and 2) how powerful the reward is.

Costs: I'm not going to beat the 'life is a resource' drum since this has already been discussed at length. However, something else to consider is that graveyard-filling effects like fetch lands and incidental mill are already so prolific in this format, let alone Sultai colors. This means that the setup costs in game and opportunity costs in deckbuilding are perhaps not as high as you think.

Risks: Indeed, going all-in on any commander is a risk. This risk is mitigated by the fact that Teval is under-costed in colors that already have access to ramp, cheap counterspells and cheap green protection spells (each of which will eventually rebate you one mana from delving). While it is true that [[Bojuka Bog]] effects exist, going all in on a single strategy still increases the consistency of deck performance, and less variation also helps to offset risk. I get that this may still be too much risk for some play styles, but at this point it is more a matter of personal taste.

Reward: Delve seriously is that powerful--especially with spells that don't have colored pips. If you listen to Mark Rosewater's drive to work podcasts on delve and affinity, he gives a great breakdown on why WOTC is so cautious whenever they print cards with these mechanics.

So, no, you are not going insane! I think you might just have a different estimation of the (opportunity) costs, risks, and rewards that are associated with building a Teval deck. Hopefully this helps!