Widely reported in the press, (Independent, Times, MEN, Talksport) as far back as April this year.
UEFA said that it (Old Trafford) does not comply with all of it's requirements.
United claimed they pulled out of the application as Old Trafford may be subject to renovations at the time of the Euro's
It was also reported as far back as 2019 as questionable by FIFA
https://www.mirror.co.uk/sport/football/news/man-utd-could-miss-out-20541537
Where did UEFA say that? Have you got anything from UEFA saying that Old Trafford doesn't comply with it's requirements? I'm presuming the list you previously gave comes from somewhere. Because if so I'm confused how Old Trafford was allowed to host two high profile UEFA internationals in the last 18 months, including the opening game of a UEFA tournament. It was reported in April that United pulled Old Trafford from the shortlist because the availability of the stadium could not be guaranteed due to the ongoing review around regeneration of the stadium, which is entirely reasonable given that it had been publicly stated that they were looking into all options regarding renovating and even rebuilding the stadium.
The article you have linked relates to supposed FIFA concerns, which would be irrelevant for a UEFA competition, and highlights the press box, mixed zone and media lounge being too small, which the club say would be easily fixed with a reconfiguration of space which in fairness is correct. The second issue highlighted is not being able to accommodate the required number of broadcast cameras and the third issue highlighted is that the away dressing room is too small, which again are pretty simple reconfigurations for a club of United's size, that would be accomplished in no time at all between a season ending and a tournament beginning.
If you genuinely believe that Old Trafford would be rejected due to the concourses being "too narrow" (which I do actually agree in some parts of the ground they are by the way) and the stairways being "too steep", I can only assume you have never been to St James Park. Similarly around "poor seating" and "poor viewing for pitchside seating", I can assume you haven't been to Hampden Park. And that's without even mentioning Villa Park which is in a comically bad state of repair. It was withdrawn, if it wasn't withdrawn it would 100% have been selected as one of the ten stadiums for the tournament.
I'm talking about events like the Euros finals and the CL final. We've not been in contention for those for a while.
The Euro's finals? Such as what? Euro 2020? Only Wembley went forward from England and it was one stadium per national. Euro 2022? Old Trafford hosted the opening match of the tournament. Euro 2028? Pulled from bid as above. Champions League finals, I don't know, have they even put in for it? How many club stadiums (that weren't built for other purposes ala Atletico and Hertha Berlin) have been used over the past decade or so? The San Siro was given it in 2015 and that is in a far worse state of repair than Old Trafford. The national football associates put the bids in, why would the FA put any stadium forward other than Wembley to host a major final?
There's no dispute that major money needs spending on the stadium to bring it into line with certain 2023 requirements, but there is also a significant exaggeration of certain issues because it suits certain agendas, which I understand.