I feel like the main problem with Tera comes down to particular users that facilitate the abuse of it.
I don't think Tera as a mechanic itself is broken.
Tera Blast is useless for almost all Pokemon and often ends up being a wasted move slot inmost matches. while a handful can make good use of it, and another very tiny percent become busted. Pokemon like

and

are perfect Tera Blast abusers because it allows them to overcome their limitations. Volc can set up to the sky and still wouldn't be able to touch Pokemon like Heatran or Skeledirge. Regieleki has monstrous speed and offenses but can't do much with it's limited coverage, however Tera Blast allows Pokemon like these to bypass their flaws and step beyond their natural boundaries.
Defensive Tera for most Pokemon is only good for living one hit and get that rapid spin, set rocks or get a single KO. However for Pokemon like

or

defensive Tera allows them to check out their weaknesses and set up on their limited checks and can proceed to brute force their way out.
STAB Tera provides a valuable tool for many Pokemon, yet for most of them is not broken because they will almost always fall short in power, speed or coverage, however for Pokemon like

and

their STAB coverage and offensive output is so overwhelming it becomes unmanageable.
Coverage Tera is another aspect that can be troublesome, Pokemon with broad hitting dual STAB like

and

can become near unwallable with a Third STAB, Bax with STAB earthquake, Valiant with Shadow Ball/knock-off and Sneasler Shadow Claw/Acrobatics with can hit for neutral or super effective damage complex dual type Pokemon that resist or take neutral damage from their both STABs. However for most Pokemon with lesser offensive stats and worse type coverage are better off defensive Tera over coverage.
I think the issues with Tera are way more layered than expected. When people complain about Tera blast, do people really complain about Tera Blast itself being broken or rather is it because a selection of sweeper and wincon Pokemon can use it to get rid of it's dedicated counters? Is defensive Tera broken or is it just a selection that can use it to set up and proceed to snowball? Is offensive tera busted considering most Pokemon aren't min-maxed offensive speedsters? Is defensive Tera busted considering most Pokemon can't effectively set up or have recovery moves?
Every issue with Tera is likely in part, tied to users with tools that can make the most of it. Tera on most Pokemon isn't busted. that's why some users don't think the mechanic should be even be touched.
Also with Tera you don't just gain advantages, Tera always opens some backdoor for opposing counter play. For example: did your Ting-Lu Tera Ghost to spin block or avoid a Close Combat? Now it lost it's ability to counter Gholdengo, did Heatran Tera Grass to survive that Earthquake? Now it loses to the flying types Hurricanes it used to counter. Enamorous became Fairy Tera to deal more damage? Now it can't switch back on Tusk's Headlong Rush without the ground immunity. Losing a type or changing type can lead to losing a front on some type match up, this is why Tera doesn't feel like a brainless easy win mechanic. Tera in some situations doesn't offer anything, Tera water Garg still loses to Grass Knot, Tera Fairy Garg still loses to Make it Rain, defensive Tera being limited to being monotype might still be useless against neutral hits from opponents dual types not resisted by a single type, specially at lower HP.
To further add to the complexity, it seems Tera affects ladder and tournaments differently, while important matches can be defined by unconventional Teras, laddering prefers long term consistency through continuous matches. In important matches, something like a gimmick Tera Electric Cinderace to get rid of a Dondozo or that SD Tera water Liquidation Iron Valiant that was used on a Volcarona team, can take important wins but aren't useful in constant laddering.
The issue with targeting Tera abusers, is that players might get upset over more bans, because OU is an ecosystem that surrounds about 5 to 7 really strong Pokemon that threaten each other. Volcarona was an example of this, Volc threatened Tusk and Gambit with burns, resisted Valiant dual STABs and threatened Gholdengo with Fire moves. Many players were upset over Voc's ban because it was their anti-meta answer for all these Pokemon despite Volc being very oppressive against almost everything else, and the departure of Volc only made Iron Valiant and the rest raise in viability... Tusk keeps Gambit in check, Gambit keeps Dengo in check, Dengo keeps Valiant in check, Valiant keeps Tusk in check... Removing elements might upset the order and this is why people aren't asking for suspects or don't take some bans well. Despite we are all well aware Pokemon like Volcarona or Kingambit aren't very fair and balanced.
Would banning Tera Blast really fix things up? Personally, as a ladder player I very rarely encounter Tera Blast, I find myself in more trouble with stuff like Stored Power or playing 50/50s with 5-fainted-allies Gambit's sucker punches, these feel more oppressive and more frequent than any Tera Blast user I ever encountered.
Will Tera on team preview fix things up? Probably, Probably not, even without Tera on preview we all know Dragonite likes to Tera normal, Gambit likes to Tera Flying, Garg likes to Tera water/fairy, Roaring Moon likes tera Flying. Tera on preview might even give off your sets: Tera Dark Valiant? Then must be physical with Knock off, Tera Ghost Valiant? Then it's Special with Shadow Ball. And the 50/50s are still there. I used to be very pro-tera preview until giving second thoughts to these points.
Complete Tera ban? Will the player base go along with this? Will they reject an offensive tool and all the possible strategies to align with the interests of the big stall mafia? Probably an unlikely scenario.
If the solution for Tera was simple then the debate wouldn't have lasted this long. Tera is a complex mechanic and likely will need complex measures to be fully balanced. I don't think simple measures will be satisfactory. But how much could the policy against complex ban be allowed to bend?