There have been tier one aggro decks that were toxic and tier one non-aggro decks that were not toxic. It sounds like you are cherry picking decks and metas that support your viewpoint and are ignoring decks and metas that go against it.
The problem with metas that are toxic is not that the toxic decks are aggro or not aggro, it's that the meta is defined by a toxic deck (regardless of archtype). The reason why that toxic deck tends to be non-aggro is because non-aggro decks almost have to be toxic to be able to go tow to tow with the aggro decks.
Edit: god I am writing far too much today, sorry about that. Also I am not trying to say other people are wrong or bad. Scholarly discussion of these things is interesting and fun to me and I have an opinion so I am stating defending and discussing it. and after a while it seems that other people are also doing so. On to the giant block of text but first tldr: I think control limits control and while aggro can be toxic it is easier to counter more consistently than other archetypes.
That is possible, in fact it is likely that I did not think through how toxic certain aggro decks were, though on further thought I care more about diversity of what is possible, and meta's with aggro decks on the top tended to, with one main exception at the beginning of naxx, have diversity. I know undertaker was the worst but I sucked then so I don't know a lot, barely got past rank 15. It was nerfed, and then as I understood it the meta got better but again if I am wrong correct me. powerful decks were still hunter and zoo and stuff but other decks were good again including midrange and control. GvG had some crazy aggro, I think not sure though because I still sucked. As I understood it though priest was great control warrior was great and there were many midrange mech decks and stuff so it was diverse anyway. then with blackrock tempo mage and patron were really powerful, with many control decks (warrior priest handlock) and some midrange (mech still I think?). some decks were toxic but the meta was diverse enough but I still sucked some getting better, rank ten some seasons with weird decks off-meta. then there was the grand tournamen which for me sucked. As for secret pladin being a fast midrange deck as someone said secret paladin played 7 and 8 drops. Yes it wanted to win by turn 9 but it did not always and it could take the game longer to a more midrange type gameplan. It started to push out other decks, patron got nerfed and secret paladin basically reigned supreme until league of explorers, where face shaman became great, face hunter had been dying a while and would get finished off in whipsers but the meta was diversifying with reno and stuff. Then with old gods I legitimately enjoyed the meta for a while until it got stale a month before kara. The meta had settled down after a month and a half of things still being up in the air because of all the changes all the different decks that were available and good around then including aggro shaman but also c'thun warrior, and c'thun warrior was the main thing that killed other control then and it beat fast decks. then kara hit and just made shaman better, which was boring because nothing else happened, shaman got nerfed and so did all the other decks so shaman still sat on top but now literally nothing else could touch it, it was tier 0 and we all hated it and it was a midrange deck, someone said this deck was fast for midrange, and it could win early, but it also could win in fatigue. it had all options covered and this is why I don't want a slower deck to be dominant. the slower the dominant deck, the more options it is able to account for and the less opportunity there is for counter-play and variety in the meta. Then gadgetzan "fixed" things by killing that deck and adding two decks to the game, and so now we had two opposite decks being dominant and that sucked. the meta was slower, but it was not more interesting, reno versus reno was randomfest, reno versus pirate was randomfest, pirate versus pirate was the most skillful matchup you saw more than once an hour. That sucked because basically anything you built to counter the best deck was beaten by the other best deck and both the decks were unfun to play unless you liked random and jades weren't great either.
Maybe my main problem is the dominant deck being highly adaptable or even just capable of more than one facet of gameplay. So if we have a single faceted control deck dominating the meta it will all be fine.
I personally just feel like aggro decks being powerful means it is more likely the top deck can be countered. and if it can be countered the meta can be diverse as play and counterplay develop around the top few decks.
I fully admit any deck can be toxic, but a meta where a deck is toxic happens more often when decks don't have counters. Aggro usually has a counter. I have played more mindblast priest than is reasonable and lost maybe 10% against aggro because I ran 2 ofs of 3 cards that counter aggro. It is possible to play weird decks when the counters to enough of the meta are simple and easy to put in any deck. The only reason why classic control warrior is bad right now is that priest and mage have so much value. Aggro is not the thing limiting playspace right now it is the midrange and control. I want more control cards and more midrange cards but I don't think that will slow the meta, I think that will diversify it but not noticeably slow it.
Essentially I feel like control limits other control more than aggro does, and midrange can be so powerful when it is the best deck that it just negates the ability for decks to counter it. That is why I want the meta not to slow down, I do want more control decks to be viable, but that just means that the specific way of doing things you face is different, not that the overall meta is slower. I want more possible control and midrange, but for aggro to still be the best deck so that no archetype is limited to a single example. You can have many aggro decks in synchrony but if the best deck is control it is hard for other control to see play.
aggro is easier to counter more consistently than other archetypes.
If you look at actual winrates it is usually the opposite. Tier one aggro decks will typically have no tier one matchups where they are heavily unfavored whereas control decks usually do.
The only reason why classic control warrior is bad right now is that priest and mage have so much value.
Control Warrior is also heavily unfavored against Jade druid and is unfavored against most midrange decks. Even if priest and mage dropped out of the meta it is unlikely that Control Warrior would be tier one.
if the best deck is control it is hard for other control to see play
That's not true. It's true that Hearthstone doesn't balance the control decks against each other very well, but that is a problem with balancing and not a problem with the archetype in general.
Just fill your deck with one drops, that is creative deck design, right?