The class is shockingly evil to me, as written, even though a few of the official patrons are not evil.
Which is perfectly fine--except that you presented your opinion, originally, as the only way to interpret the text--and told others
they had to "redefine things" in order to get their opinion. In other words, as with several conversations before this, you held up the books as supporting your perspective and making your perspective "right." Then...
The discussion here has shown a lot of sharp disagreement, becoming vitriol in reply to my own comments, which oddly are among the shortest. The primary issue of contention seems to be whether the text means the same thing for everyone who reads it, and whether that text is the highest authority.
...you say things like this, once people cite the text and demonstrate that your argument either doesn't fit the text as-written, or is a personal interpretation of the text rather than its explicit meaning. Also, whether a post is short or long has nothing to do with whether it is inflammatory--and some of your posts, whether you think it or not, have been inflammatory.
Is it so bad to be told you would have to be evil to be a typical warlock of the fiend or great old one? If the DM doesn't allow any evil PC's, then it could be a big downer because then you'd have some players who like it but can't play it. I recommend letting the alignment of the patron match the warlock.
No, it is not so bad to have that--in fact, several people responded to your initial "it has to be evil, it's even more evil than assassins and necromancers!" post with, "Well sure, Infernal pacts are almost surely evil, and GOO pacts aren't necessarily much different, but surely the Fey pact doesn't have to be evil?" So you're retreating to the position others originally took in opposition to you, and acting as though it is a call to reasonableness against people who are being unreasonable.
That said, your last recommendation is very solid--and mirrors, perhaps ironically, the way that Paladins worked in 4e. Paladin was the only class (IIRC) that had any kind of "alignment restriction" in 4e: you had to start out with the same alignment as your god. You could change later on, and nothing would directly change (but you'd probably have your church after you for heresy if you changed dramatically). Warlock, whether 4e or 5e, seems to fit a similar mold. I could see someone arguing for being "within one step" of their patron's alignment--so a Lawful Neutral person could potentially make a pact with a Lawful Evil entity--but just straight-up matching to patron alignment makes perfect sense.
That said though--yeah, it would be pretty bad if one was gung-ho about playing a GOO or Infernal Warlock and couldn't because the DM essentially banned those classes. "I don't permit Evil PCs" + "GOO and Infernal pacts are only for Evil characters" = "GOO and Infernal pacts are banned at my table." It may not be explicitly said, but it's a deductive consequence of the previous two statements. There is no case where the first two statements are true and the third statement is false unless the DM makes a special exception (which would mean, more or less, violating either the first rule, allowing an evil PC, or the second rule, allowing a GOO/Infernal pact Warlock that wasn't evil.) Any situation which eliminates player enthusiasm about non-abusive, rules-as-intended play is something I consider "pretty bad."