Vivaldi, played badly, is the worst classical music on earth

Right you are, Al. Classical immediately followed Baroque (Renaissance proceeded Baroque, Romantic followed Classical).

The early practitioners of "period" Baroque performance (now referred to as historically-informed) were faulted for their lack of technique and spotty intonation (playing in tune), as well as what was considered by the old guard as the "ugly" tonality of Baroque-style instruments.

The demands of Classical music, orchestras, and concert halls, required a change in the design of orchestra instruments, to make them louder and to project more. And Classical music was performed with far more string vibrato than was Baroque, and by far more instruments (Symphony Orchestras are comprised of FAR more instruments than are Baroque). Classical was also generally written to be performed at slower tempi than was common in Baroque. Conductors and orchestras over the years started performing Baroque music in the Classical style: too slow (slower than the markings on the scores), and with too much vibrato.

No, the early period performers weren’t as precise as their major orchestra peers, but they were playing the music closer to how it had been written to be played. The movement and it’s practitioners have progressed to the point where historically-informed musicians are now amongst the best in the world. And the movement has forced the conservative, old guard conductors, orchestras and their musicians, to join in, performing the music as the composer intended.

There are still those who prefer Baroque performed as they have heard it their whole lives, by a Symphony Orchestra. Each to his own!

The historically-informed movement has worked it's way forward in time, addressing both Mozart and Beethoven. For anyone who has found Classical music to be boring, listen to it in a "period" performance! In place of the slooow, lethargic, ponderous, "schmaltzy", easy listening style of Bruno Walter and Herbert von Karajan, give a listen to it done by, say, John Eliot Gardiner.

The conductors and orchestras of the early part of the 20th century were actually closer in style to period performers than were those of the mid-century. Toscanini played Beethoven fast! Too bad his recordings were made before good equipment was available: their sq is pretty bad.   

Most people use the term Classical for ALL "serious" music, but it is, as has been noted, a particular style and time period in "long hair" music.

There are quite a few great recordings of Le Quattro Stagioni, as well as other Vivaldi's compositions. I like those of Trevor Pinnock directing The English Concert (his original analog recording on CRD, his second digital on Archiv), and Jaap Schroder directing Concerto Amsterdam (Harmonia Mundi).